What is this amplifier doing, exactly?

oric_dan:
Well, actually, not "quite" a Class A design. Class A is intended to bias the transistor
into its linear region of operation, but you'll never get that with the ckt as shown.

It looks like the person who designed it had the intent of Class A, but you would need
a resistor in the emitter lead, so the 100Ks on the base have something to bias in
a stable fashion. As it is, they simply turn on the transistor, and whether or not the
collector sits at Vcc/2 is strictly a factor of the hFE [beta] dc current-gain of the
transistor.

Advice - throw this ckt away, use something better.

Sure it's Class A. Class A is defined as bias current flowing all the time. Class A doesn't HAVE to also be "linear".

And, given the choice of Class A, Class AB, Class B, Class C or Class D, what would YOU call it? :slight_smile:

The emitter resistor isn't really needed because the bias-stabilizing negative feedback comes from the fact that the top base resistor is connected to the COLLECTOR and not to VCC.

I agree though, that circuit is better off in the trash can! :slight_smile: