
Principles of Analog Electronics
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10.2.4 Class
The amplier efciency depends on the so-called “class” of the amplier. We
distinguish four classes in analog designs: A, B, AB, and C. Differences are related
to the amount of variation of the output signal for a full cycle of input signal, as in
Figure 10.4.
The classes are dened as follows:
➜ Class A: The output signal varies for a full 360° of the cycle of the input
waveform.
➜ Class B: The output signal varies over one-half, that is, 180°, of the input
signal cycle.
➜ Class AB: The output signal swings between 180° and 360° of the input
waveform.
➜ Class C: The output signal varies less ...