Chapter 1 – Before we begin (Preliminary information)
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In order to keep this book to a manageable number of pages, the author assumes that the reader has already studied the basics of electronics, such as Ohm's law, passive electronic components (resistors, capacitors, and so on), has experimented with electronics to some extent already, can do basic soldering, and can read schematics. This is not an introductory electronics book; rather, it fills the void created by all other “introductory” electronics books in discussing transistors and semiconductors.
If the reader has not yet developed a basic love for electronics, then I highly suggest that the reader joins one of the local electronics groups. Websites such as Meetup.com can be used to find local groups.
For preliminary reading, and for introductory electronics books, I can recommend such titles as:
Practical Electronics for Inventors, by Paul Scherz
Old books on electronics and semiconductors from your local city, college, or high-school library. Books written in the 80's are, in my opinion, much better than modern super-expensive, thick, impractical books with equations and calculus to memorize.
I highly recommend for the reader to pick up any used college textbook on the subject of basic circuit analysis. Ignore treatment of semiconductors, if any, calculus, and any electronics concepts you have not heard about before and will never use. Many books are available, such as “Basic Engineering Circuit Analysis” by J. David Irwin. There is absolutely no need to buy the expensive hard-cover latest edition. Used, previous editions, soft-cover, and “international” versions are always cheaper.
My website, http://www.MKRD.info/SemiconductorsBook, has articles, a forum, and a user-editable wiki about everything electronics (among other things).
I highly recommend one of the kits for ease of experimentation, such as the RadioShack “Electronics Learning Lab” (28-280, $70) and similar kits such as PL300 300-in-one kit (Ramsey Electronics, $110).
1.1 Interpreting and drawing a circuit
Modern electronics has gotten lazy and liberal with drawing schematics. I wish to have the reader follow the traditional standards to make life easier for anyone who will have to interpret the reader's schematics. All circuit lines showing connections must be straight lines only. Transistors must have circles around their symbols. Connections between two or more wires must be indicated by a dot. Input is on the left, signals flow in the direction of text (to the right), and output is on the right. Power supply should be on the right. Circuit elements should be aligned to each other vertically and horizontally. If two circuit symbols need a COMMON connection, and are close together, then they must be connected together. Component identifying information should be present, and placed neatly next to the component.
Whenever possible, symbols must be upright, especially transistors. Devices must be evenly spaced and snapped to grid. Polarity must be indicated on capacitors with a plus sign, in addition to using a polarized symbol.
Only the standard and traditional symbols must be used. This is very important, so I have placed the symbols on the front cover of the book! The second reason is so that others know you are not reading a love story novel. If they ask you what you are reading, lift the book up and show them the cover.
Use symbol identifiers which are standardized and consistent, and are neatly next to the symbol. When a BOM (bill of materials) is not attached to a circuit, then properties of the device (part number, power rating, parameters and specifications) should be listed. This will help to analyze a circuit without having to pull up all of the datasheets for every single component. List required ratings next to the symbol, but also list a recommended part number.
Use subscripts to generalize circuit devices by their intended function.
For example: DF 1N4001 1A 1W. This means a "flyback diode", 1N4001 recommended, required circuit rating is 1A, 1W power dissipation. While a voltage is not given, it is assumed that it is easy to interpret from the circuit, is of low consequence, or should be that of the 1N4001 device, if a different device is used.
1.2 Engineering notation
This book will use many different types of engineering notation.
The first notation type is the SI prefix. Voltages and currents such as kV, mA, μA will be thrown around, and the book assumes that the reader can interpret the meaning.
The second notation type is symbol identifiers. As I have just mentioned, for circuit analysis convenience, every symbol should have a subscript identifying the component's purpose. For example, CB is a bypass capacitor, Rp is a pull-up resistor, RE is an emitter resistor, RESD is a resistor, and it is plain that the resistor serves an ESD protection duty, and so on.
Voltages and currents will have subscripts as well, to identify measurement conditions. If a single subscript is used, it signifies a voltage at a particular point in circuit, or the current thru that point. For current values given, or if a current must be measured, imagine breaking the schematic wire connection and inserting an ammeter at that point. For example, VE is voltage at the base, while IE is emitter current. If two subscripts are used, it is a differential measurement between those two points, or a combination of a specifying symbol and a measurement at that point. For example, VBE is voltage from base to emitter. VRE is voltage at the emitter resistor. We are not using a sub-subscript in the latter case because the print would be too small. Two subscripts repeated signify a voltage at that point, usually with a reference to COMMON. This is most often used to specify a power rail: VCC or VDD is “+” positive supply rail, while VEE or VSS is “–“ negative, or COM (COMMON) supply rail.
Three subscripts indicate a differential measurement and the condition for the measurement. For example, VDSS means voltage from drain to source, with the condition that the gate is shorted to source. The measurement condition is usually memorized or given elsewhere on the component datasheet.
Additionally, a measurement condition is sometimes specified in the subscript. IF @ TJ=100°C is diode forward current at a junction temperature of 100 °C.
This notation does require some skill to interpret, but greatly saves space and time when used and understood properly.
1.3 Black-box conventions used throughout the book
In order to make our study of electronics progressive in difficulty and intuitive, we will take a step-by-step learning process. The first time devices will be presented in this book, they will be in the form of a black box. Here, the term means “something that we do not know how it operates inside, but we can get an understanding by observing how it operates by connecting it in a test circuit and seeing how it behaves”. These are vastly simplified symbols; no one in the industry uses such symbols, and you will not see them elsewhere, but I hope that the reader will thank me for not confusing the reader with too much information up-front.
1.4 Devices used in this book's examples
I will be using many components in this book which can be bought at your local RadioShack store. The reason should be obvious – you can obtain a component immediately most hours of the day. There is no need to spend an hour browsing around, get distracted at random websites, pay for shipping, and wait a week. Besides, personnel at the store will be able to help you.
When a part is needed which is not available at a RadioShack, I will recommend a cheapest thru-hole part with best parameters, from Digi-Key. Although I am not a fan of Digi-Key blowing my money advertising in inappropriate places (Popular Mechanics and Wired magazines – wth?), but they have good selection and I always use their online product selection tool. Other electronic parts distributors exist – if that part is available somewhere else, do support the other guys as well (Arrow Electronics, Allied Electronics, Jameco, Mouser, Futurlect (parts straight from Asia), All Electronics (overstock/unwanted/used parts), etc).
You certainly can buy components as you encounter a circuit which uses them. But that would cost you greatly, in separate shipping and waiting costs of each separate order. The complete list of important components used in this book which are not sold at RadioShack are available on my website. It will be of value to put an order for these before you begin your study, so that you do not wait afterward. I also highly recommend to instead purchase a components kit from me, so that you do not have to waste the time looking, overpaying (I purchase my components in bulk quantities), and waiting for shipping (I always use fast shipping). Purchase the kit from my website.
Datasheets for devices illustrated in the book
Every electronic device has an accompanying datasheet, which lists all device parameters, along with other useful information. Datasheets are obtained from the parts reseller online, from the manufacturer, on an online database such as AllDataSheet.com. I have created a single compressed file containing all of the needed datasheets for the book. The file can be downloaded from the book's accompanying website, http://www.MKRD.info/SemiconductorsBook
Handling and soldering. Electronics is sensitive to ESD. Care should be taken to limit ESD at all times when working with electronics. For storage and movement, an electronic component must be placed into a non-ESD bag (those shiny silver-looking ones you have seen when purchasing electronic or computer parts). During soldering, a controlled temperature must be applied to an electronic part, and not for a longer amount of time than the datasheet specifies.
Identifying an electronic component
That is done by finding the device part number. Semiconductor manufacturers do not show any willingness to make device identification intuitive or standardized. Some skill is required. Starting point in learning how to identify components is with datasheets (last pages usually decipher labeling) and known devices. A device usually has a label which contains the part number, manufacturer logo, date code of manufacture (usually a four-digit code composed of the number of the week of the year and the year of manufacture, for compactness), place of manufacture, letters or numbers after the part number signifying a sub-variation such as temperature or speed limits, etc. Confusingly, the most important of them – the part number may not even be on the first line!
1.5 Test equipment
Note: all test equipment listed below are Chinese-made white-label units. White-label means that the manufacturer does not place their name anywhere on the unit, giving up that right to other companies who slap their sticker on the unit, and proclaim it to be made by them. For the cheap equipment listed, search by the part number, not the brand name. I have listed recommended brands or websites as a reference only. Most of these units can be bought on many different websites and under other brand names.
DMM (digital multi-meter)
Fig 1.1
The most affordable and universal DMM is a VC99+ ($35-40, it must have a carrying case, AideTek.com). The features in a DMM you should look for are: 10A current measurement capability, autorange, transistor test, capacitor test, frequency measurement, secondary display or readout, min/max storage, diode check, and continuity check, among others. A full-featured meter is recommended over cheapo construction, high asking price local retail store units.
You will also usually need a second multi-meter when you need to measure more than at one point. I highly recommend that you get an analog (needle) multi-meter, often referred to as VOM. Using an analog meter requires a little more knowledge and skill than a DMM, but it is precisely that skill and knowledge which needs to be gained. Additionally, analog meters are often more intuitive and are more suitable to see varying phenomena (seeing a capacitor charge, adjusting the power supply, rotating a pot, etc), than a cold, emotionless, and too-precise digital numbers reading. A meter from a local store or an old unit will suffice.
Ammeter
Fig 1.2
I will insert this ammeter symbol at points of a circuit when we will need to know how much current flows thru that point in the circuit. For the purposes of circuit analysis, a good digital ammeter at a large current measurement range (10A) is a short, or a straight wire connection from one DMM lead to another. The circuit would see that straight wire short, and not even know that a DMM is there. Therefore, practically any wire in a circuit can be disconnected (“cut in half”), a DMM inserted, and we would know what current flows at that point, without impacting circuit behavior by doing so.
Power sources
Batteries are not at all recommended for circuits which you build. Besides being expensive, they are not current-limited, do not last long, and do not supply a constant voltage level. The most affordable choice for a power supply is a “wall-wart” power supply. Everyone has plenty of wall-wart power supplies that no one knows what they belong to (how hard would it be for the manufacturer to slap on an identifying sticker???).
I have listed power supply schematics in chapter 7.
The first one converts a wall-wart or a laptop power supply to a variable voltage, variable current, and creates an electronically protected power supply.
The second utilizes a power supply from a used or discarded computer, for a very powerful but cheap power supply.
Schematics for both are available. Both can also be purchased from my website, either as kits, or as completely built units.
Fig 1.3
However, what separates a casual experimenter from a serious one is an adjustable-voltage adjustable-current power supply with at least a 24V and 3A capability. Thankfully, a variety of cheap, used or Chinese units, are now available for purchase. I recommend the power supply pictured. Its specifications are 0-30V, 0-3A. It is a white-label unit, so it goes under several different brands and model numbers. One is available for $90 on MPJA.com.
I use several different power source types for circuits presented in this book. They are:
Fig 1.4
Constant voltage source: Like a battery or a fixed voltage bench power supply, these will supply a known and constant source of voltage for the circuit.
Fig 1.5 Variable voltage source: To analyze circuit behavior, a variable voltage source will be used. Voltage from such a source can be set to an arbitrary level, or varied continuously. For example, a circuit may be evaluated if a voltage source is varied from zero to 12 volts.
Load
For practical circuits, a load will always be used in theory—illustrating circuits throughout the book. Several types of different loads will be used in this book. You are highly encouraged to build all of the circuits which are illustrated in the book. There is nothing better than to learn electronics with a hands-on approach!
More advanced equipment
If you are rich enough, or find a deal cheap enough, the following equipment is very valuable:
Oscilloscope (“scope”). Recently, this is possible to do right on your computer with a USB unit.
Signal generator. There is an intriguing signal generator being manufactured in Hong Kong and sold on e-Bay for about $80. It is based on a single chip, an AD9850. Get one with the enclosure (pictured), a test probe, sweep function, and a power supply. This is cheaper than buying a used professionally-made signal generator.
Parallax Professional Development Board
Fig 1.6 Single-chip signal generator
Soldering smoke absorber. mpja.com 15166 TL, $28
ESD preventing mat and wrist strap kit. 276-2370, $27
Rosin core flux (cannot be used with SMD). 64-022, $7
Desoldering braid or wick. 64-2090, $4.19
Desoldering iron. 64-2060, $11.59
Vacuum desoldering pump. 64-2098, $15
Rosin core solder with silver. 64-013, $7
Breadboard. 276-056 or 276-002, $15
Hookup wire, multicolor, 22AWG. 278-1224, $7.49
Breadboard jumpers kit. 276-173, $6.19
Cheap multi-bit set (any type with many bits). 888A-38pcs, $10
High-quality stainless steel tweezers with a good grip
Breadboard style PCB. 276-150, $2.19
Mini PCB. 276-148, $2.19
Combination flush cutter and wire stripper. 64-080, $15
Chisel tip. mpja.com 15852 TL, $1.95
Medium tip. mpja.com 15849 TL, $1.95
Plenty of jumper wires and banana to alligator/grip wires. 278-001, $8 (and others)
Tip tinner and cleaner. 64-020, $8
150/300W soldering gun. 64-2187, $33
500-Piece 1/4-Watt carbon-film resistor assortment. 271-312, $13
Storage cabinet with bins
Harbor Freight, 91310, $10
Wire sponge tip cleaner, All Electronics, $9
1.6 Tools
A large collection of tools is something that is not bought, but collected over a period of time, as you find what exactly you need, and as you buy the tools which you come across. Do not attempt to buy everything at the same time (that's expensive). I highly recommend that the reader first joins or creates a hobby electronics club, and then buys the tools with the combined input of the whole group, so that tools can be shared. There may also be a local tool lending library (not a book library!). Nevertheless, what you are buying are valuable tools, and not consumable or disposable useless items. There is little sense in me listing every tool you need, besides the two previous pages listing (part numbers given are for RadioShack). Other tools which are specific to electronics work are:
A large collection of jumper wires, mini-grabbers, banana to alligator as well as banana to grabber patch wires, probes, and miscellaneous wire
Jeweler's screwdrivers and bits set. I only ask the reader to never buy a screwdriver set which looks like the picture on the right. Whoever has designed this has never held a screwdriver in their life. You will often need to press hard on top of the screwdriver to unscrew something, and the idiotic cap on top will cut into your palm. Also do not buy the RS 64-071 set. The cheap plastic handle will break easily.
Good light over your work area
Magnifier
A collection of miscellaneous parts
A collection of miscellaneous parts
Our society is one of a disposable mindset. Everything is expected to cost cheap as dirt, is not expected to last any particular amount of time, and everyone is expected to buy the same thing again when it comes out with more features a year later. That leaves a lot of disposed electronics, which may or may not work, but which is very valuable for examination, by the process of taking the devices apart. This collection of electronics is also a valuable source of wall-wart power supplies, mechanical parts, miscellaneous electronic components, and desoldering training material.
Soldering
Fig 1.8
A piece of equipment which states that you are serious is a temperature controlled soldering station with a grounded tip soldering iron, and an interchangeable set of tips. Again, used and Chinese units are cheap, such as the unit pictured on the left ($47, mpja.com). It is sold under many possible brand names, such as Tenma and ZD Electronic Tools. Always purchase a set of different size and shape tips at the time you buy a soldering station, such as the 0.02" rounded tip and 0.08" chisel tip for this particular station. Also get desoldering attachments for your soldering station, such as mpja.com “hot tweezers adapter and tip set” for the station pictured on the left.
Other soldering equipment which you will eventually buy because you will really need it was listed on the two pages listing previously.
Soldering techniques are covered at length in my other book, Michael's Guide to Soldering. I will briefly cover some of them, but soldering is a skill you learn and earn by supervised practice, not by reading about it. Again, your local support organizations, or an electronics mentor / friend will help you with this.
Soldering is a very precise process, and there is only one way to do it right. I have seen it done wrong in a million different ways.
The right way to solder:
Set the temperature—controlled soldering station to the right temperature. This temperature depends on the type of solder used, and is within 400-650°F. Wait for the tip to come up to the set temperature.
Select a proper solder and flux type. Refer to my book on soldering.
If the tip is very dirty (because you overheated it and left it un-tinned for a period of time), use a specialized tip cleaner.
If the tip is lightly oxidized, has old solder from the previous session on it, etc - clean it off by inserting it into a tip cleaning wire sponge, not the junky wet sponge. Every time I look at a wet sponge, it is dry, and if there is a water container next to it, it is moldy, and the wet sponge cools down and thermally stresses the tip when used.
Select a proper tip size. Contrary to what everybody intuitively thinks, the power of a soldering station is not adjusted by adjusting the temperature. What typically happens is that the soldering station was bought with a tiny SMD-sized tip. It is more than likely black from oxidation. And then the user tries to solder a large component, and the solder does not melt. Do not try to remedy the situation by adjusting the heat even higher! That will only cause more oxidation and tip damage! Temperature control is there to adjust for different soldering alloy types and to set the temperature to an exact value. It is not for “wattage control”. If there is poor thermal transfer, then the tip is not clean enough and does not have a light coating of shiny solder. If the soldering iron takes a long time to solder a large part with a clean tip, then a larger tip should be used. The “wattage” of a soldering station is adjusted by physically swapping the tip. A very fine tip is used for SMD work, but a larger tip is needed to transfer enough heat to larger components.
Apply a small amount of flux to the connection to be soldered. Flux used must be specific to electronics. Household (plumbing, etc) flux is not at all acceptable for electronics work. If that connection has not been pre-tinned, then it should be (PCB silver-looking pads and clean, new electronic component leads are considered pre-tinned or not requiring tinning). If it is two pieces of copper wire, etc which need to be soldered together, then they need to be pre-tinned.
Touch the connection which is clean, pre-tinned, and has a small amount of flux with a tip which is of a proper size, at a correct temperature, that is clean and has a light coating of shiny solder. Shortly afterward, the flux will melt and clean the connection. A short amount after that, solder at the connection will be heated up by the tip. This can be seen visually by observing that the solder brightens up and starts flowing. As soon as this happens, touch a flux-core solder to the joint, and have enough melt to cover the connection which needs to be soldered. Remove the soldering iron and give the connection ten seconds to cool down without moving it.
Solder joint which you have made must be shiny. Dull looking joint is a cold joint (look it up), and indicates an incorrect temperature or soldering procedure.
Clean off any excess remaining flux with a Q-tip dipped in alcohol. Any flux remaining on a connection will corrode that connection over a length of time. Not using too much flux beforehand will ensure that an excessive cleanup is not needed afterward.
The secret to The Only Proper Soldering Method is “Heat connection first, and then apply solder”. The opposite method, done by most amateurs or lazy-heads, is not acceptable. The second secret is “Use a little flux. Pre-tin wires and bare-metal surfaces”.
SMD soldering requires good eyes, a magnifier, small tip, thin solder, solvent based flux, and steady hands, but it is getting harder and harder to cling to thru-hole parts only.
A note on working with wiring
Do not ever use electrical tape. The only proper way to secure two wires to each other is by soldering them together, and applying a heatshrink tube over them. The only proper way to attach a wire to a board is with a bolt-down connector, or by soldering it to the board.
Crimping two wires is a quick and dirty solution, but it will not make a reliable connection. Whenever two dissimilar metals are in contact with each other, there will be galvanic corrosion (look it up). Over a length of time, that contact between two dissimilar metals will deteriorate and become unreliable. You may have noticed that copper wire is often crimped into silver-looking crimping connectors. Using a little flux and solder on the crimp connection will make it much more reliable. Note that all of the flux has to be cleaned off the connector when you are done soldering, or the flux itself will cause corrosion as well.
Whenever connecting two wires or a wire to a connector, wire gauge must not be changed. Aftermarket automotive electrical parts and cheap retail electrical appliances illegally violate electrical code:
Fig 1.9
The switch here is a breaker which will only trip if more than 20A flows thru it (15/20/25A, depends on its rating). As an illustration, consider this: a cheap appliance was bought which used small-gauge wiring. A 0Ω short develops in the appliance. However, because of the small wire size, the wire has a small resistance of its own. That resistance causes the breaker to see a resistance of the short (0Ω) plus the resistance of the thin wire. If the resistance of the thin wire is more than 6Ω, the breaker will never trip. However, the large current will be flowing thru the thin wire, heating it up. A combination of a large current, a thin wire, and a length of time will cause an overheating, melting, and a possible fire.
I do not understand how cheap Asian-made appliances are allowed to be illegally sold in retail which violate NEC electrical wiring code and may cause a fire. More so because the mechanical parts of the cheap appliance (switch, bulb base, insulation, etc) are in my personal experience very prone to failure.
1.7 Choosing a correct resistor
The most important concept to know when using resistors is tolerance. For example, a typical thru-hole resistor will have a tolerance of 5%. This means that the actual resistance of one resistor from a batch will be within the range of -5%...+5% relative to the claimed resistance. For a 1k resistor, you will find individual resistors with values anywhere from 950 to 1050Ω. This teaches us three good lessons:
1) A circuit cannot be built in the hope of having its parameters set by exact values of its components.
2) The high precision of a modern calculator cannot be taken literally when designing a circuit. If the result of your final calculation is 39.377777989, then you need to use good sense by not expecting this precision from your circuit.
3) A circuit containing many components will be within a ballpark of your calculations, but will never produce exact values and behavior due to the combined tolerance effects. Don't expect exact behavior from the circuit.
There are also 1% tolerances and better, but they cost more than 5% carbon film.
Table of standard values
Due to the 5% spread, a set of standard resistance values was created. Any arbitrary resistance value should be within 5% one of the “standard” values. Therefore, when a result such as 39.377777989 is obtained from the calculator, the reader needs to choose a closest value from the table which is within 5% of this calculation.
10
11
12
13
15
16
18
20
22
24
27
30
33
36
39
43
47
51
56
62
68
75
82
91
These values can be multiplied or divided by powers of ten to obtain values in the ohm, kilo-ohm, and mega-ohm ranges. For example, 1.1Ω and 110MΩ are both listed as “11”.
Parallel and series connection
Values from the table above can also be combined in series and/or parallel combinations.
For two resistors wired in series, Rtotal=R1+R2
For two resistors in parallel,
For multiple resistors in parallel,
Wattage
Resistors also have wattage specifications which must not be exceeded. At any power level less than the device maximum, the temperature of the device will increase due to the wattage of the heat dissipated, but will not exceed a maximum temperature level.
Power dissipation in a resistor can be calculated from , or , where voltage is across the device, or current is thru the device.
1/4W and 1/8W are common thru-hole device ratings. These can be easily identified by their size.
1/4W. 1/4" long
1/8W
Fig 1.11
Color code
Typical 1/4W resistors are labeled with a color-band code, due to their small size. Two bands specify the first and second digit of the value, and the third band specifies the multiplier.
Band color
1st, 2nd bands
3rd band multiplier
4th band color
Tolerance
Black
0
x1
Red
±2%
Brown
1
x10
Gold
±5%
Red
2
x100
Silver
±10%
Orange
3
x1k
Yellow
4
x10k
Green
5
x100k
Blue
6
x1M
Violet
7
x10M
Grey
8
Gold. Divide by 10
White
9
Silver. Divide by 100
Fig 1.12
A lesson on precise resistor values
Recently, someone has told me to run a few measurements with two power resistors, 49 ohm, 1% and 499 ohm, 1%. I can guess how those values came about. Someone has set up a test, and needed a resistor value. They have picked a nice round number, 50. Since there are no common standard (5%) 50 ohm resistor values, they went to a table of 1% resistor values available, and picked the nearest number, 49 ohm. They then brought along the 1% tolerance that the table of values listed.
I was the one who had a problem. Follow the discussion along with your full attention! My problem was the lack of 49 ohm and 499 ohm resistor on hand. I could certainly order them, but that would cost me and I would need to wait several days. I went to the spare parts drawers and looked around for available parts. I had lots of 50 ohm resistor on hand, but I could not actually use it. Why? Because the specification called for 49 ohms ±1%. That would mean an acceptable range of values from 48.49 to 49.49. Notice the constraint that was placed on me: I could not actually use a resistor value which was picked in the first place!
Since I have a head on my shoulders, I had at least a few solutions to the problem.
The easiest solution is what no textbooks teach you: that values of old resistors drift outside of their precision % tolerance values. I was able to find 50 ohm 1% resistors which were actually 2% out of the precise value, due to age.
The second solution, of course, is to connect a resistor of much higher value in parallel, to bring the resistance down to 49 ohms. Since my specification called for 2W power resistor, I had to calculate the second resistance value (and pick a resistance within a 5% standard value), and calculate the power dissipation required for the second resistor. Both of these tasks are left for the reader as an exercise.
The third option was a series connection of two power resistors. If I manually went thru all the 25 ohm parts we had on hand, I could easily pick two with lower resistances to get the 49 ohm required resistance.
There were several other ways out of this problem remaining. One additional way is to use an adjustable resistor, which we had on hand as well. I leave it as a task for the reader to come up with other solutions to the problem.
The reader should now realize that there are several meanings for the "precision resistor" phrase. The least practical meaning is the fact that you can have a precise resistor value you wanted. What is the problem with using precision resistors instead of 5% ones? Cost, of course, and lack of on-hand availability. 5% resistors are only as far away as your resistor collection or the nearest RadioShack.
There are few cases where circuit operation must rely on a precise resistor value, with op-amps being prime examples. If the gain of an op-amp is set by three resistors, and all three have 5% tolerance, then the exact gain can vary too much for precise circuits.
Notice also that if we built a non-critical circuit, and have used 1% precision resistors for four out of five needed resistors, but used a 5% for the fifth one, then that wouldn't make much sense. Because money was wasted without gaining precision: that single 5% resistor reduces the circuit path precision to the worst resistor tolerance.
In this book I will only use 5% resistors, and I will always assume that a nearest 5% standard value will be used, if I specify a non-standard resistor value in a calculation.
The tolerance of most measurements and circuits that the reader will come across will not care whether 5% or 1% resistors are used, because other conditions will affect the precision to a larger extend. The reader must be aware of this, and use common sense to realize that all numbers shown in this book, in the real world, are subject to change of 5% or more.
The case of the burning-out potentiometer
Perhaps the most abuse that resistors get comes from ignorance of resistor power dissipation. Relevant equations are and , where V is the voltage across the device. Either equation can be used. The reader should remember to calculate power dissipations for all low-resistance (less than 500Ω, at our low voltages) resistors in schematics.
Trouble comes when potentiometers are used. In experimental circuits, potentiometers are often connected from power supply to COM, with the wiper being connected to load, like:
Fig 1.13
For a connection like this, there is both a static dissipation of, as well as a variable dissipation of I2*R, where I is the current to the load. For a linear, resistive load, potentiometer dissipation is easy to calculate.
This connection will be used in the book as a “poor man's voltage or current source”. The current to the load is limited by , while Vload varies with the potentiometer position.
There's a more dangerous application, however. Many semiconductor devices we will discuss in this book are non-linear devices. In experimental circuits, currents thru semiconductor devices should be approximated before connections are made. This approximation is difficult because semiconductor devices are not linear.
Consider the case of me burning out potentiometers, something that I suspect has been done a countless times by others. I would connect a potentiometer in the “variable resistor” configuration (wiper connected to one side of the potentiometer, and two wire connections coming in – see picture below). Experimenting, I would start rotating the potentiometer. Nothing interesting would happen; the load (such as a diode, LED, or BJT base) would not come on. Then, suddenly and instantly, the potentiometer would go poof!, with appropriate noise, smoke, and smell of burning. That's a dead $3 potentiometer. Invariably, this happens at the low resistance setting (wiper is close to the lead which is not connected to that wiper).
Fig 1.14
The problem is nonlinear semiconductor behavior and operator ignorance of maximum resistance power rating. The diode below the variable resistor is a non-linear device. As you can see from the plot, the current thru the device does not start to increase much until the point of voltage VF across the device. After that point, current thru the device increases very fast. Exponentially, in fact. The fact that power thru the device increases as the square of current only adds to the agony. It is easy to see now that as the potentiometer is rotated, nothing much would happen until the critically low resistance setting. Right after that resistance setting, the current thru the resistor, due to the “load” diode will increase extremely fast, and rotating the potentiometer to just a little lower resistance will instantly exceed its maximum power rating, destroying it.
By the way, that power dissipation is given for the whole potentiometer. If the wiper is rotated to half the resistance, only half of the internal resistive material is dissipating the heat, and maximum power dissipation rating of the potentiometer must be halved. At low resistances, a very small section is able to dissipate the increasing heat. I highly suggest for the reader to take apart one of the large potentiometer and see how it works.
To test for a dead potentiometer, first measure resistance between the two non-varying terminals. If you do not get a reading, then the pot has been burned out. Then connect an analog (preferably) or a digital meter from the wiper terminal to one of the other two terminals. Rotate the pot from minimum to the maximum, and watch out for any sudden resistance changes or jumps. If there are any, then the pot can be thrown out.
Old potentiometers wear out as well. After prolonged use, the wiper is no longer securely contacting the resistive strip. In the old days of analog potentiometers controlling audio volume, you could hear this as “scratching” noise as the volume is adjusted.
1.8 Capacitors
I assume that the reader knows the basics, and I will only cover aspects which are always ignored by textbooks (lack of practicality?).
Capacitance has lower tolerance than resistance. Standard capacitance precision is ±10%.
Electrolytic capacitors age quickly. Any restorer of old radio or amplifier equipment knows that electrolytic capacitors must be replaced after perhaps 20 years, since they become useless over that period. Their electrolyte dries out. This is also the reason why old capacitors should not make it into the reader's spare parts collection, because they cannot be trusted.
Capacitors do not tolerate high temperatures, be it either ambient, or due to large pulsating or AC current flowing thru them. A common sign of a dead capacitor is its bulging cap. This is often seen in power supplies, where large capacitors are used.
Capacitors store charge even after power is removed from the circuit. A hobbyist or experimenter should never touch or attempt to desolder large or high voltage capacitors (found in power supplies, TVs, photo cameras, etc). Before working on a circuit which has been relatively recently unplugged, an insulated 100Ω power resistor must be placed across (with the aid of an insulated handle or insulated pliers, not bare fingers!) capacitor leads for three seconds.
Electrolytic capacitors (look like a can or a barrel) are polarized capacitors. That means that they have required polarity: “–” indicated on the capacitor must be connected to “–” of the circuit. A capacitor which is incorrectly connected will heat up and explode. Perhaps you have noticed the shiny uncovered cap of the capacitor with a deep line across. That is a designed-in weak point in case the cap blows.
Few textbooks ever mention electrolytic capacitor voltage ratings. Capacitor size and cost increases quickly with increasing voltage rating (for the same capacitance). In general, a margin of 1.5x times the peak or maximum voltage that the capacitor will be working at is a good minimum voltage rating.
There are also non-polarized capacitors of various sorts. In general, capacitance less than 1μF are made with non-polarized capacitors. There is a cross-over range of 0.1μF – 3.3μF, where capacitors of either type can be used, provided that voltage requirements are met. Above a couple of μF, non-polarized capacitors would be physically too large, so only electrolytic capacitors are used for high capacitance. In the cross-over range, depending on what you need, either type is used, with the restriction that an electrolytic capacitor would have polarity requirements. Textbook formulas often spit out a capacitance answer, but they do not tell you whether it's an electrolytic, a non-polarized capacitor, etc. It is up to the reader to use the head on the shoulders.
Here's a reward for the reader – something which few non-professionals know. It is possible to make a capacitor of high capacitance, which is not polarized:
Fig 1.15
Capacitor tolerance
Standard capacitor tolerance is 10%. The table of standard values is listed below:
10
12
15
18
22
27
33
39
47
56
68
82
Fig 1.16
Capacitor voltage rating
Capacitors must not be operated at a voltage higher than their rating. For circuits with AC or varying DC voltage, that means any maximum or spike voltages which may appear across the capacitor. As a rule of thumb, capacitor voltage rating must exceed maximum voltage it will encounter in the circuit by 1.5 times.
1.9 Logarithms and logarithmic behavior
Audio-taper potentiometers
It has been determined that our hearing follows a logarithmic response: our ears can differentiate loudness levels between two very faint sound levels, but as loudness increases, there is less relative response. At very loud sound levels, a relatively large level change is needed for the ear to differentiate the level difference.
Audio loudness is expressed in dB (decibels), a logarithmic unit. deci- is, of course, a prefix meaning “ten”. Bel is the actual mathematical logarithmic unit of relationship. The lower limit of auditory threshold is taken as 0dB, and permanent hearing loss is somewhere around 120dB. However, since a dB is a logarithmic unit, the upper “120dB” number is actually a 1,000 trillion times more louder (linearly) than the auditory threshold of 0dB.
From this, we can conclude that:
A) The human ear was designed to be the most amazing auditory input device, with an unbelievable dynamic range of response
B) Increases from a loud music to very loud music have little effect, and are just a source of wasted power, distortion, noise pollution, and hearing damage
I urge the reader to always wear hearing protection when operating power tools and compressed air tools. Also, I urge the reader to not wear “over the ear” headphones, and to not listen to loud music with headphones. Additionally, do not go to rock concerts where music is turned to hearing damage levels, with the only intent of programming the sheeple.
Back to the audio-taper. Because the hearing response is logarithmic an “audio taper” logarithmic response potentiometer is used in audio amplifiers. Its resistance varies like
Fig 1.17
So that at 50% of rotation, the ear perceives loudness to be half of 100% rotation. The audio-taper potentiometer is not used outside of audio applications. Our circuits will use linear taper potentiometers.
As a side note, if you have ever had a cheap electronic appliance, which had a volume adjustment behave the opposite way, you now know the reason. Notice that the audio taper potentiometer must have all three terminals connected in an exact way. The terminal near the nearly-horizontal response must be connected to COM, and the nearly-vertical to the input source. I had a radio which did the opposite – loudness increased quickly and suddenly as the volume control was adjusted slowly from “min” setting, while little change was heard when adjusting from the medium setting to “high/max”. They connected their potentiometer in reverse!
Comparing loudness
Due to the logarithmic ear response, comparing two audio power levels is not an algebraic operation. The equation which calculates a relationship between two power levels is:
dB
For example, 16W is 2 times louder than 4W. There is a lessons to be learned here. For a small increase (doubling) in loudness, amplifier power and speaker rating must be quadrupled. For example, if 4W is a sufficient volume, then there is no need to go any higher in power. Wasted electrical power, and expensive amplifier and speaker are the results of going louder than necessary.
Potentiometer letter identifier
A potentiometer may have an identifying letter after the resistance value, signifying whether it is of a linear or logarithmic type. Unfortunately, due to stupidity, these letters are not standardized, and are different in the US from Europe or Asia. The letter “A” may mean an Audio or Log taper, the letter B may mean a Linear taper, and the letter C may mean a Reverse Log taper.
Audio Loudness comparison table
Jet engine at 30 m, Rock concert
150 dB
Threshold of pain
130 dB
Hearing damage (possible), shotguns and rifles
Approx. 120 dB
Jet engine at 100 m, Disco
110 – 140 dB
Jack hammer at 1 m
Approx. 100 dB
Traffic on a busy roadway at 10 m
80 – 90 dB
Hearing damage (over long-term exposure, need not be continuous)
85 dB
Passenger car at 10 m, vacuum cleaner
60 – 80 dB
EPA-identified maximum to protect against hearing loss
70 dB
Handheld electric mixer
65 dB
TV (set at home level) at 1 m
Approx. 60 dB
Washing machine, dishwasher
50-53 dB
Normal conversation at 1 m
40 – 60 dB
Very calm room, mosquito
20 – 30 dB
Light leaf rustling, calm breathing
10 dB
Auditory threshold at 1 kHz
0 dB
Fig 1.18 (Wikipedia)
Logarithmic plots
Fig 1.19
Here is an example of a semi-log plot (log-linear). Notice that the y-axis is a logarithmic scale, obvious from the uneven distribution of ticks. The scale counts off powers of ten. The y-axis goes from 0.8*10-1=0.07 to 10 (three orders of magnitude). The benefit of a logarithmic plot can be seen: a very large range of data was compressed into a small graph.
Fig 1.20
Here is an example of a log-log plot of a quadratic function f(x)=x2.
Besides being able to fit a large scale of values, there are two more reasons log-log plots are used in science and engineering:
1) For ease of taking precise measurements from the plot
2) To illustrate that the plotted phenomena is of a logarithmic nature. In science, data is often collected and plotted without knowing the underlying mathematical relationship (equation). Now that we see a linear plot, we can then assume that an equation of a logarithmic nature is the underlying cause of this data.
3) For ease of extrapolation of data. Notice that the plotted data does not reach the top of the plot. Perhaps a scientific experiment gathered some data, but data at x=10 could not be gathered. We can then quite easily extend the linear line to the x=10 point (heavy dot), and read off the y-axis resulting value (100).
To summarize – the reasons log plots are used are:
To represent behavior over a very large range (perhaps a million times spread)
To show that behavior is a logarithmic function.
For ease of taking precise measurements from the plot (by linearizing it)
However, intuitively, it is hard to understand circuit behavior from a logarithmic plot. If you want to intuitively grasp device behavior, try to find and look at linear-linear plots instead.
1.10 Safety
Physical Safety: Circuits in this book can have a light bulb explode into your eyes, a resistor, the MOSFET, the bulbs, or the soldering iron burn your fingers, or a motor cut your skin. Be smart and wear personal protective equipment.
Electrical safety and a third of a dozen different Grounds
Ground
Before we can discuss safety issues, we must go over some concepts.
“Ground” in electronics is an overly abused word. In its common use, it actually has nothing to do with the physical ground under your feet.
Let us explore the following circuit (we will ignore its pointlessness):
Fig 1.21
We see two voltage sources: VS1 and VS2. Their positive terminals are connected to different parts of the circuit, but the negative terminals are tied together. Several additional components are connected to the same point in the circuit. This special part of the circuit is called a “common”, or by the improperly used term “ground”. All currents travel thru this “common” point to return to the power supplies.
Additionally, all voltages are usually specified with a reference to this “common” point, for simplicity. For example, if you were asked to measure the voltage at C1 north, you will assume that it is from the north lead of C1 (on top), to COM.
Since many components connect to the same point, a COM line would run thru the whole circuit. Having to draw a COM line to every component which is connected to it is not always convenient or pretty-looking. There is an option to attach a “COM” symbol, as was done for R4 and C3, which would mean that R4 is directly connected to the same COM point which R2 south is connected to, etc.
Differential measurements
Using a portable hand-held and battery-operated DMM, it is easy to take measurements across or thru any component in the circuit above. If we wanted to measure the voltage drop across R1, we could place the black and the red DMM leads on the two component leads and read off the voltage. If the voltage was we read from the DMM was negative, we can just interpret that as our assumption of where we should have placed the red DMM lead being incorrect.
However, using a benchtop-style DMM or an oscilloscope is very different. There is no such thing as a “+” and “–“ oscilloscope leads. There is a GND lead, which is always at 0V potential (more on this in a bit!), and an input lead. If a measurement was made across R1 by placing the tip of the oscilloscope at R1 north and the ground clip at R1 south, then the ground clip of the oscilloscope will ground (bring to 0V potential) the R1-R2 point of the circuit. If the circuit's COM potential is at the same potential as the oscilloscope's GND potential (they are both interconnected by a wire, or thru the AC outlet), then if VS1 was of high voltage and high current capacity, and R1/R2 were low resistance values, then the oscilloscope will pass a lot of current thru itself, and blow the instrument fuse and house breaker. Even if the circuit was low-powered, we would ruin its operation by grounding the R1-R2 point.
Don't go sticking that GND of a benchtop (non-battery-powered) instrument anywhere other than circuit common! The only safe way to measure voltage across R1, is by use of two channels and probes of an oscilloscope, and a math “differential” feature. There are also expensive “differential” probes for a single channel available.
Alternatively, the “GND” connection of the scope to the Earth ground protection feature can be disabled, with an isolation transformer. The isolation transformer is plugged into an outlet thru a “cheater plug” (which converts three prongs of the outlet to two prongs with the earth disconnected). The scope is then connected into the isolation transformer. This disconnects the scope chassis from the Earth ground for both the “neutral” and “earth” wires.
We will look at AC currents for a while, and then we will return back to discussing grounds.
AC Voltage Safety
Household outlets contain a very dangerous electrical current. It is an AC current (sine wave), with an RMS voltage value of 120VAC, and breaker current of 15-25A.
The human body can pass current (it can act as a resistor), but that resistance is highly variable. Skin moisture, contact area, hydration level, and many other factors can greatly affect that resistance. You can see this for yourself by grabbing the two leads of a DMM in a resistance check mode, with fingers of each hand. The resistance goes down the harder you press on the probes, because the area of contact changes.
If someone was careless enough to ever come in contact with a wire carrying household AC current, then there are two or more possible current paths. The first possibility is for the current to pass thru the body and into the ground (any surface) that person was standing on. Obviously, the clothes and shoes the person was wearing and the ground condition would determine the total resistance.
A more dangerous condition is to have current pass thru the chest, by entering into one hand, and existing thru the other. Very low currents can cause heartbeat to become erratic or to stop completely. This is why it is not recommended to work with both hands, should the reader ever have to work on an AC circuit (after proper training and certification, of course!).
An additional risk factor with AC is the fact that the current is quickly changing its polarity. If someone ever grabbed AC carrying wire with their palm, their muscles would twitch many times a second, and that person would get a muscle spasm, and would not be able to release their grab from the wire.
Another health risk from household AC current is the high amount of current flowing thru the wires, up to 25A on 120VAC line (up to 50A on 250VAC outlets). If a piece of metal, or thin wire was to contact the hot wire, it would cause a spark, welding of the shorting metal to the conductor, great amount of heating (up to red hot), and pieces of molten metal flying. 25A is a HUGE amount of current, higher than anything the reader has encountered before from benchtop low-voltage power supplies.
Besides the breakers (if your house uses fuses, get an electrician to rewire it), a wonderful safety feature for household appliances is the grounding connector. The modern outlet has three connections: hot (or line), grounded (formerly called neutral), and grounding wires.
Fig 1.22
Electrical poles carry either one or three high-voltage wires, with voltages of 6kV typical. If three wires are used, then a three-phase system is being used. I have supplied two wires to the transformer primary for simplicity. That “6kV” must, of course, be specified relative to some voltage point. That reference point is the Earth potential. It is assumed that the Earth can carry unlimited amount of current back to the electricity generating facilities, all of which have their current “return” connected to Earth. Since we are using a transformer on the pole (that big bucket, which can feed a whole street), its secondary is completely electrically isolated. Therefore, we must have it connected to Earth again. There is a wire running down into the earth on every pole with a transformer on top. Then, two wires are connected from the pole to your house. Both wires are “hot” - they carry 120V each.
Your house, in turn, has its own “Earth” connection, with a metal rod buried outside the house, and a connection to the incoming water pipe, both of which have a very good connection to “Earth”. The “hot” wire, is passed thru two breakers on to the outlets. But then you see that the grounded (neutral) and “ground” wires are connected together at the breaker panel. Why?
Fig 1.23
For safety reasons. Consider the Figure on the left, which is a crude equivalent of a household appliance. We see a three-prong plug with a grounding connector, a metal housing of a typical appliance which is connected to the grounding wire, and a grounded line, which is connected uninterrupted (uninterrupted by a switch or a fuse) to the load inside the appliance.
Consider the very real possibility that the metal casing has its insulation from the circuit deteriorate and break down, and a connection results between the metal housing and the incoming hot wire. Consider that the grounding (“Earth” or “Ground” in the old nomeclature) wire was not present, because the house electrical system was old and was wired to old standards. The metal appliance metallic casing would then carry a dangerous 120VAC potential, and when someone touches it, they will get a dangerous shock, because their body would create a path from AC hot wire to ground (any surface) they are standing on.
You can now see that the “neural” does not prevent the person from being shocked. Now consider that the metal case is connected to the grounding wire. If any part of the circuit, carrying a potential above 0V, touches the case, then that current will be carried away by the grounding wire, which will short-circuit that potential to ground potential. No dangerous AC potential will be present on the metal casing if the grounding system works properly. This is the reason for the new NEC chosen terminology: the previously-named “neutral” wire has been renamed to “grounded” connector, because it is always connected to earth at the breaker panel. The “grounding” wire is only “grounding” a voltage potential if something goes wrong, and it is not supposed to carry currents in normal operating conditions. The grounding wire up to recently was called the Earth or Ground wire.
Another household safety device is a CGFI breaker, which must be installed in kitchens near kitchen sinks, in bathrooms, unfinished basements, and whenever a water or moisture source is present. This safety device will very quickly interrupt the flow of current if it senses a small difference between the current supplied (thru the hot wire) and the current returned (thru the grounded wire). Why is a CGFI breaker is needed? Because if an appliance happened to perhaps fall into a tub with a human inside, then the high resistance of the water will cause current from the “hot” wire to flow thru several paths. One path will be into the grounded wire, but due to high resistance, the low additional current (besides the load inside) will not trip a conventional breaker.
A second path of current would flow into the grounding wire, but not all of the current will take the path. A remaining path is thru the water, which will be at 120VAC potential, and into the human inside the tub.
A CGFI does its job by monitoring the levels of currents in the hot and the grounded wires. Any discrepancies can only mean that the current is finding another way – perhaps thru a person touching the appliance, or thru the water which the appliance fell into. A CGFI breaker will then quickly disconnect the flow of current and prevent a death.
The reader should now see that if they reside in a house wired to old standards with outlets without grounding wire, then they should have their house rewired to modern standard, by a licensed electrician. CGFI outlets or breakers must also be used according to the code.
The reader should now grasp the concept of a ground as a common reference point, and as a safety feature. Back to our low-power electronic circuits, we now realize how idiotic it is to use the term “ground” without there being a real connection to the ground. This confusing terminology is freely accepted in electronics, however. The much better term to use is “common”, because that is precisely what that special circuit potential is.
Since the term is so overly abused, it must be clarified when used, to be of use. There can be several types of “grounds”, for physical reasons. There can be:
Fig 1.18
Circuit ground. For battery-powered circuits without a connection to Earth, a more proper term is “common”. The American circuit GND symbol is:
Fig 1.19
I have a problem with this symbol. Instead, I will be using a European “common” potential symbol, which does not imply any connection to real “ground” or “Earth”. It looks like an inverted power rail symbol, or the American GND symbol without the extra lines.
In this book, any time the circuit is not physically connected to Earth ground, this symbol will be used, and it will be referred to as “COM” (common). For most circuits, the mis-named and mis-represented GND symbol and its designation will be equivalent to this book's “COM” symbol and designation.
Fig 1.20 Chassis ground
For circuits housed in a metal enclosure, there is also the “chassis ground” – a connection to the conductive metal part of the chassis. This can be done for electrical safety and EMI shielding reasons.
Fig 1.21 Earth Ground
And finally, for circuits which require an actual connection to Earth (perhaps audio equipment or ESD protection equipment, which is connected to a separate buried rod in the basement of the building). The symbol for real Earth Ground is pictured on the right.
In my humble opinion it is idiotic I have to resort to this work-around.
Benchtop power supply terminals
Fig 1.22
A good power supply has three terminals. The third terminal accessible to the user is usually of green color, and has a Ground or Earth symbol. It is connected to the metal chassis of the power supply, to the earthing terminal of the plug, and to the Earth Ground.
The “–” terminal is not connected to the chassis or the earth. It is “floating”. This allows power supplies to be connected in series, with the “+” of one power supply connected to “–” of another one.
However, if the user wishes to have their circuit grounded, then a jumper is placed from the “–” terminal to the GND terminal, but at that point, the power supply is no longer floating, and the “+” is only specified to the Earth 0V potential, which the black terminal is forced to be fixed to.
Electrical isolation
Every circuit which the reader will work with must be on the opposite side of a transformer plugged into the AC outlet. A transformer, such as that of a power supply, is doing the function of isolation. There is no electrical connection from the transformer secondary to dangerous AC currents in the primary windings:
Fig 1.23
This circuit is the equivalent of every compact power supply. The right side of the dashed line has no connection to the AC-carrying left side.
This circuit design is “floating”. For example, the “–” of this power supply can be connected to the “+” of another power supply, to have two power supplies in series for double the voltage.
For safety and electrical noise shielding reasons, an oscilloscope GND probe clip is forced to be connected to the scope chassis, which is itself connected to the grounding plug connector. The reader should now see what would happen if the GND scope clip was connected to the “+” of the Grounded power supply, or a circuit which was not isolated from AC with a transformer: what that would effectively do is create a short from power supply's “+” and “–” terminals, since the scope GND clip is connected thru the Earth to the “–” terminal. That scope could physically be in another side of the room, and on a wire feed from another electrical pole, of course, since the two Ground potentials are interconnected anywhere on the surface of the Earth.
As a final reminder about grounds, the user should remember that “common” reference point of every circuit which is connected to other circuits must be connected together with the other circuits. Because a return path for current is required, two wires are always needed to establish current flow between two different circuits or devices. This also applies to everything else connected to the circuit, such as power supplies, signal generators, test equipment, and so on.
Capacitor-based transformer-less power supplies
Fig 1.24
Do not ever build a circuit like this. This is an extremely dangerous configuration. This circuit is not isolated from the AC “hot” line with a transformer. Additionally, in order for this circuit to produce a proper, low output voltage, it must be loaded with a guaranteed load of an exact resistance. If this circuit is not loaded, then its output voltage becomes higher than the input line voltage. Attempting to use a DMM to measure unloaded voltage will result in DMM damage (for non-autoranging types). Being unfortunate enough to touch the output side of this circuit when it is not loaded will result in an electric shock. Also, should the loading circuit ever draw less power than needed, or should the voltage regulation feature of a circuit of this type fail, then the load will be exposed to the full line voltage. This will definitely result in the destruction of all devices in a circuit connected to such power supply.
Let's begin exploring semiconductors!
