# Class AB amplifier

What role does Rv play in this AB class amplifier?

This is a class B amplifier: -

Your circuit is a class AB amplifier: -

Rv adjusts the bias point of the two transistors so that T1 and T2 are always conducting a little bit of current - this avoids excessive cross over distortion: -

• Your diagrams are misleading. For the first one, the Q point would be slightly below the X axis because of the $V_{BE}$ drop of the transistors. You need the "small bias" just to get to true "class B" operation. "Class AB" would be what you get with even more bias, in which both transistors are conducting some amount of current all of the time. – Dave Tweed Oct 15 '15 at 12:41