Two Transistor Class A Transformer Coupled Audio Amplifier

This is a demonstration of two transistor audio amplifier that can amplify the audio output from a smartphone to drive a 5 Watts speaker. The two transistors work as a common emitter class A audio amplifier. Class A transformer coupled audio amplifier amplifies the signal with least distortion. The input signal is fed to the first transistor amplifier, here it voltage amplifies the small signal coming out from the phone. The common emitter class A amplifier amplifies the full portion of the audio waveform and it has little to no distortion. The amplified output signal is then fed to a second power transistor through a coupling capacitor. The second power transistor, which is also a common emitter class A amplifier further amplifies the signal. The collector output from the transistor is then fed to a loudspeaker through an audio transformer. This audio amplifier can provide about 5 watts of power. The collector voltage can be increased from 12 volts to 15 or 16 volts to get more power output. Make sure to provide enough heat sink for the transistors.
This simple audio amplifier provides clear sound that is distortion free and the transformer coupling provides efficient output coupling to the loudspeaker. This audio amplifier can be used for smart phone audio amplifier applications that drives a low power low impedance loudspeaker. It can also be used for small audio amplifier system that helps amplifying the output of small public address system, musical instruments, audio oscillators, alarms, toys etc.