ANALOGUE ELECTRONICS I

A class B circuit provides an output signal varying over one-half the input signal cycle, or for 180⁰ of signal. That is, an amplifier is biased at cutoff so that it operates in the linear region for 180⁰ of the input cycle and is in cutoff for 180⁰.   This is illustrated below:

Obviously, the output is not a faithful reproduction of the input if only one half-cycle is present. Two class B operations—one to provide output on the positive-output half-cycle and another to provide operation on the negative-output half-cycle—are necessary. The combined half-cycles then provide an output for a full 360° of operation. This type of connection is referred to as push–pull operation. Note that class B operation by itself creates a very distorted output signal since reproduction of the input takes place for only 180° of the output signal swing.