A 10mV(Max) sine wave is input on the left. This is amplified by the circuit to produce a 400mV(Max) output sine wave!
The Capacitors on the left and right keep the 12V DC flow within the amplifier. The two 30K resistors form a voltage divider, keeping the Base of the NPN transistor at 5V so it is always switched on.
The Capacitor in parallel with the 764 Ohm resistor lets the AC current flow to ground with much less resistance whilst the DC current flow must go through the 764 Ohm resistor, holding the voltage at the Emitter at 2.3V.
Also the Emitter resistance is set to 8.31 Ohms, in keeping with the Forward Beta of 300A/A.
The minimum specified frequency of this amplifier is 100Hz.
