A true Class AB amplifier

432

07:25:49

A true class AB amp should consiat not only of a current amplifier (the push pull stage) but also a class A stage (the mosfet). The way class AB amps work is that for small signals (when the output does not reach the maximum peak power) the class A part works in the linear part of its characteristic providing low distortion and only little power drawn because it only amplifies signals below a certain threshold.,whereas a class B amp would only add crossover distortion at lower levels. Once the power rises beyond a certain threshold the push pull amp kicks in and relieves the class A amp. These amps often have efficiency levels of around 50%.
3.2W (average drawn) for 1.65W in 4ohms so around 50% efficiency.

published 11 years ago

paposo

11 years ago

Exelente circuito, no puedo dejar mas que buenos comentarios,practico y funcional

lorki

11 years ago

Sorry but no. The definition for an AB amplifier is a Class B amp with a working point nearly to class A.

hurz

11 years ago

Yes @lorki, this is also my understanding of the classes. Class B can be modified to be a class AB. @buggzy this is a class AB amp but it is already much to complicated to explain the classes and your explanation about "kicks in push pull" and thresholds for lower power is even wrong. You have here a push pull plus a class A driver stage and plus a feedback loop. But to understand the class differences this all is not needed. Whats needed is just a class A a class B and a modified B to class AB.

thebugger

11 years ago

For a class AB amplifier smaller signals are not amplified by the class B stahe but rather via a different class A stage where at these (low) power levels inefficiency is acceptible but quality can be increased. Its logical for a class AB amp to have a class A stage into it.

hurz

11 years ago

Btw, after i had a more closer look at this amp I have to say this is a class B power stage amp with class A driver and feedback. This is not a class AB

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