MULTISIM REQUIRED 1 Design a class B power amplifier complem

*MULTISIM REQUIRED* 1) Design a class B power amplifier (complementary pair) that A) delivers 50 watts to an 8ohm load. B) Show values of the components and verify theoretical formulas.

Solution

If the collector current flows only during the positive half-cycle
of the input signal, it is called a class B power amplifier.
In class B operation, the transistor bias is so adjusted that zero signal collector current is zero i.e.
no biasing circuit is needed at all. During the positive half-cycle of the signal, the input circuit is
forward biased and hence collector current flows. However, during the negative half-cycle of the
signal, the input circuit is reverse biased and no collector current flows.

the operating point Q shall be located at collector cut
off voltage. It is easy to see that output from a class B amplifier is amplified half-wave rectification.
In a class B amplifier, the negative half-cycle of the signal is cut off and hence a severe distortion
occurs. However, class B amplifiers provide higher power output and collector efficiency (50
60%). Such amplifiers are mostly used for power amplification in push-pull arrangement. In such an
arrangement, 2 transistors are used in class B operation. One transistor amplifies the positive half-
cycle of the signal while the other amplifies the negative half-cycle.