In class B operation the transistor is so biased that zero signal collector current is zero. Hence class B operation does not need any biasing system. The operating point is set at cutoff, as illustrated in Fig. 1 & 2. It remains forward biased for only half cycle of the input signal i.e., its conduction angle is 180°.
Fig. 1
Fig. 2
As illustrated in Fig. 1 & 2, during the positive half cycle of the input ac signal, the circuit is forward biased and, therefore, collector current flows. On the other hand, during negative cycle of the input ac signal, the circuit is reverse biased and no collector current flows.
Advantages:
(i) Very low standing bias current. Negligible power consumption without signal.
(ii) Can be used for much more powerful outputs than class A
(iii) More efficient than Class A.
Disadvantages:
(i) Creates Crossover distortion.
(ii) Supply current changes with signal, stabilized supply may be needed.
(iii) More distortion than Class A.
Advantages:
(i) Very low standing bias current. Negligible power consumption without signal.
(ii) Can be used for much more powerful outputs than class A
(iii) More efficient than Class A.
Disadvantages:
(i) Creates Crossover distortion.
(ii) Supply current changes with signal, stabilized supply may be needed.
(iii) More distortion than Class A.
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