# Single Transistor Amplifier Circuit

An audio amplifier is a device which multiply an applied input signal amplitude to a level that may be much higher than the input signal. The input is given in the form of an audio or a music. The amplifiers are classified into classes like class A, class B, class AB, class C and class D. Here we are going to  discuss the first type of amplifier i.e. class A amplifier and also learn how to build a single transistor amplifier circuit class A.

Amplifiers are generally very efficient because these amplifiers conduct only during the presence of an input signal and they only boost input signals. Single transistor amplifier are very low power amplifier ans consume very low energy even a single battery of low amperes can be used to run it many hours.

We want to make clear these types of amplifiers are very easy to built but the quality of mini amplifier circuit is not very good.

Single transistor amplifiers are also know as The common emitter amplifier is widely used due to very easy circuit to design. A simple single transistor amplifier dramatically boost audio input to output.

### Components required

• Transistor 1  any NPN type
• A resistor 4.7k
• Speaker 3w 4 ohm
• capacitor 10uf 16v

### Calculations

Vout = R2 * R1 + R2 * Vin

Re-arrange formula

R1 = R2(Vin * Vout − 1)

Here speaker is R2, that is 8Ω, Volts in (VIN) is 5V and Vout is 2.83V. So alternate the values and we have:

R1 = 8(52.83 − 1)

### 12 volts Amplifier

The given below circuit diagram is perfect for 12 volts. The quality and output of this circuit is much better than the circuit given above for 4 volts. In this way you can change speakers as well as resistors according the formula.

### Circuit Diagram

Given below circuit diagram is 12 volts single transistor amplifier circuit.

### 9 volts Circuit Diagram

The given below circuit diagram is calculated form of single transistor amplifier for 9 volts battery. It is also low power and low consuming energy amplifier.

## 3 thoughts on “Single Transistor Amplifier Circuit”

1. How many watts is the 9volt diagram? Also for 9volt diagram – Is the transistor getting hot or not?

1. its 2 watts amplifier transistor can get hot so you should use heat sink with it and thanku so much for feed backs and watching my article
plz always keep me visit i will be great full to you thanx dear

2. its 2 watts no this transistor will not heat because this is power full transistor