INTRODUCTION

This e-book contains 100 transistor circuits. The second part of this e-book will contain a further 100 circuits.

Most of them can be made with components from your "junk box" and hopefully you can put them together in less than an hour.

The idea of this book is to get you into the fun of putting things together and there's nothing more rewarding than seeing something work.

It's amazing what you can do with a few transistors and some additional components. And this is the place to start.

Most of the circuits are "stand-alone" and produce a result with as little as 5 parts.

We have even provided a simple way to produce your own speaker transformer by winding turns on a piece of ferrite rod. Many components can be obtained from transistor radios, toys and other pieces of discarded equipment you will find all over the place.

To save space we have not provided lengthy explanations of how the circuits work. This has already been covered in TALKING ELECTRONICS Basic Electronics Course, and can be obtained on a CD for $10.00 (posted to anywhere in the world) See Talking Electronics website for more details: http://www.talkingelectronics.com

Transistor data is at the bottom of this page and a transistor tester circuit is also provided. There are lots of categories and I am sure many of the circuits will be new to you, because some of them have been designed recently by me.

Basically there are two types of transistor: PNP and NPN.

We have labelled the NPN transistor as BC547. This means you can use ANY NPN transistor, such as 2N2222, BC108, 2N3704, BC337 and hundreds of others. Some circuits use TUN for Transistor Universal NPN and this is the same as our reasoning - the transistor-type is just to let you know it is not critical.

BC557 can be replaced by: 2N3906, BC327 and many others.

Don't worry too much about the transistor-type. Just make sure it is NPN, it this is the type needed.

If it is an unknown transistor-type, you need to identify the leads then put it in the circuit.

You have a choice of building a circuit "in the air," or using an experimenter board (solderless breadboard) or a matrix board or even a homemade printed circuit board. The choice is up to you but the idea is to keep the cost to a minimum - so don't buy anything expensive.

If you take parts from old equipment it will be best to solder them together "in the air" (as they will not be suitable for placing on a solderless breadboard as the leads will be bent and very short).

This way they can be re-used again and again.

No matter what you do, I know you will be keen to hear some of the "noisy" circuits in operation.

Before you start, the home-made Speaker Transformer project and Transistor Tester are the first things you should look at.

If you are starting in electronics, see the World's Simplest Circuit. It shows how a transistor works and three transistors in the 8 Million Gain project will detect microscopic levels of static electricity! You can look through the Index but the names of the projects don't give you a full description of what they do. You need to look at the circuits. And I am sure you will. KIT OF PARTS

Talking Electronics supplies a kit of parts that can be used to build the majority of the circuits in this book.

The kit costs $15.00 plus postage.

Kit for Transistor Circuits - $15.00

A kit of components to make many of the circuits presented in this eBook is available for $15.00 plus $7.00 post.

Or email Colin Mitchell: talking@tpg.com.au



The kit contains the following components:

(plus extra 30 resistors and 10 capacitors for

experimenting), plus:



3 - 47R

5 - 220R

5 - 470R

5 - 1k

5 - 4k7

5 - 10k

2 - 33k

4- 100k

4 - 1M

1 - 10k mini pot

1 - 100k mini pot

2 - 10n

2 - 100n

5 - 10u electrolytics

5- 100u electrolytics

5 - 1N4148 signal diodes

6 - BC547 transistors - NPN - 100mA

2 - BC557 transistors - PNP - 100mA

1 - BC338 transistor - NPN - 800mA

3 - BD679 Darlington transistors - NPN - 4amp

5 - red LEDs

5 - green LEDs

5 - orange LEDs

2 - super-bright WHITE LEDs - 20,000mcd

1 - 3mm or 5mm flashing LED

1 - mini 8R speaker

1 - mini piezo

1 - LDR (Light Dependent Resistor)

1 - electret microphone

1m - 0.25mm wire

1m - 0.5mm wire

1 - 10mH inductor

1 - push button

5 - tactile push buttons

1 - Experimenter Board (will take 8, 14 and 16 pin chips)

5 - mini Matrix Boards: 7 x 11 hole,

11 x 15 hole, 6 x 40 hole, surface-mount 6 x 40 hole board or others.



Photo of kit of components.

Each batch is slightly different:





There are more components than you think. . . plus an extra bag of approx 30 components. The 8 little components are switches and the LDR and flashing LED is hiding.

In many cases, a resistor or capacitor not in the kit, can be created by putting two resistors or capacitors in series or parallel or the next higher or lower value can be used. Don't think transistor technology is obsolete. Many complex circuits have one or more transistors to act as buffers, amplifiers or to connect one block to another. It is absolutely essential to understand this area of electronics if you want to carry out design-work or build a simple circuit to carry out a task.



We also have an eBook: THE TRANSISTOR AMPLIFIER with over 100 different transistor circuits . . . proving the transistor can be connected in so many ways.



oooooooooooooooooooooooooo00000000000000000000000000000ooooooooooooooooooo Here's an Indian eBook of 270 Circuits: Some circuits work, some don't, some are poorly designed and some use components that you cannot obtain.

But it's a good example of how: NOT TO DESIGN A CIRCUIT and HOW NOT TO DRAW A CIRCUIT.

You will learn a lot about poor circuit-design by looking through this .pdf. It is 20MB

270 MINI ELECTRONICS PROJECT WITH CIRCUIT DIAGRAM



oooooooooooooo00000000000000000000000ooooooooooooooooooooo THEORY Read the full article HERE (the Transistor Amplifier eBook)

The first thing you will want to know is: HOW DOES A TRANSISTOR WORK?

Diagram "A" shows an NPN transistor with the legs covering the symbol showing the name for each lead.

The transistor is a "general purpose" type and and is the smallest and cheapest type you can get. The number on the transistor will change according to the country where the circuit was designed but the types we refer to are all the SAME.

Diagram "B" shows two different "general purpose" transistors and the different pinouts. You need to refer to data sheets or test the transistor to find the correct pinout.

Diagram "C" shows the equivalent of a transistor as a water valve. As more current (water) enters the base, more water flows from the collector to the emitter.

Diagram "D" shows the transistor connected to the power rails. The collector connects to a resistor called a LOAD and the emitter connects to the 0v rail or earth or "ground."

Diagram "E" shows the transistor in SELF BIAS mode. This is called a COMMON EMITTER stage and the resistance of the BASE BIAS RESISTOR is selected so the voltage on the collector is half-rail voltage. In this case it is 2.5v.

To keep the theory simple, here's how you do it. Use 22k as the load resistance.

Select the base bias resistor until the measured voltage on the collector 2.5v. The base bias will be about 2M2.

This is how the transistor reacts to the base bias resistor:

The base bias resistor feeds a small current into the base and this makes the transistor turn on and create a current-flow though the collector-emitter leads.

This causes the same current to flow through the load resistor and a voltage-drop is created across this resistor. This lowers the voltage on the collector.

The lower voltage causes a lower current to flow into the base and the transistor stops turning on a slight amount. The transistor very quickly settles down to allowing a certain current to flow through the collector-emitter and produce a voltage at the collector that is just sufficient to allow the right amount of current to enter the base.

Diagram "F" shows the transistor being turned on via a finger. Press hard on the two wires and the LED will illuminate brighter. As you press harder, the resistance of your finger decreases. This allows more current to flow into the base and the transistor turns on harder.

Diagram "G" shows a second transistor to "amplify the effect of your finger" and the LED illuminates about 100 times brighter.

Diagram "H" shows the effect of putting a capacitor on the base lead. The capacitor must be uncharged and when you apply pressure, the LED will flash brightly then go off. This is because the capacitor gets charged when you touch the wires. As soon as it is charged NO MORE CURRENT flows though it. The first transistor stops receiving current and the circuit does not keep the LED illuminated. To get the circuit to work again, the capacitor must be discharged. This is a simple concept of how a capacitor works. A large-value capacitor will keep the LED illuminated for a longer period of time.

Diagram "I" shows the effect of putting a capacitor on the output. It must be uncharged for this effect to work. We know from Diagram G that the circuit will stay on when the wires are touched but when a capacitor is placed in the output, it gets charged when the circuit turns ON and only allows the LED to flash.



1. This is a simple explanation of how a transistor works. It amplifies the current going into the base about 100 times and the higher current flowing through the collector-emitter leads will illuminate a LED.

2. A capacitor allows current to flow through it until it gets charged. It must be discharged to see the effect again. Read the full article HERE

INCREASING THE VOLTAGE

You can change the voltage of many circuits from 6v to 12v or 3v to 6v without altering any of the values. I can see instantly if this is possible due to the value of the components and here's how I do it:

Look at the value of the resistors driving the load(s). Work out the current entering each load and see if it is less than the maximum allowable.

Then, take a current reading on the lower voltage.

Increase the voltage to the higher value and take another reading.

In most cases the current will increase to double the value (or a little higher than twice the original value).

If it is over 250% higher, you need to feel each of the components and see if any are getting excessively hot.

If any LEDs are taking excessive current, double the value of the current-limiting resistor.

If any transistor is getting hot, increase the value of the load resistor.

In most cases, when the voltage is doubled, the current will will crease to double the original. This means the circuit will consume 4 times the original energy.

This is just a broad suggestion to answer the hundreds of emails I get on this topic.

