Electronic – Push-pull Amplifier Class AB

amplifierpush-pull

I am new to electronics and I am trying to build an audio amplifier with an input signal of 100mV @ 60 hz using 12V as VCC and expect an output of 70-75W power.

I have the following circuit:
enter image description here

I copied this one from my notes and simulated it just to find out that it does not amplify. I believe there is something wrong with the biasing. What could be the problem?

Best Answer

Its not the biasing - in fact there is no problem.
That circuit is not a voltage amplifier, its a current amplifier - the key feature being that both of your transistors are configured as emitter-followers (gain ~ 1).

What you have there is a common configuration for the output stage of an audio amplifier because it can drive lots of current into your speaker.

You need to add a voltage gain stage in front of it in order to amplify your 100mV signal into something that the output stage can use.
The easiest way is to cheat and use an opamp...

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