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.
- Transistor 1 any NPN type
- A resistor 4.7k
- Speaker 3w 4 ohm
- capacitor 10uf 16v
Circuit Diagram 1
Vout = R2 * R1 + R2 * Vin
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.
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.