The DC input power, heat generation and maximum thermal resistance of class A and B amplifiers are calculated. We know that the AC output power is 200 Watts, and that the Class A and Class B amplifiers operate with the maximum theoretical efficiency. We also know that the BJT power transistor has a maximum junction temperature of 155 degrees C, if the ambient temperature is 25 degrees C. The calculated results indicate that the Class A amplifier is an enormous power waster in comparison to a class B amplifier.© BrainMass Inc. brainmass.com October 25, 2018, 9:05 am ad1c9bdddf
First, it can be shown that the maximum theoretical efficiency of a class A and B amplifier is 25% and 78.5%, respectively. As the efficiency equals the AC output power from the amplifier divided by DC power supplied to the amplifier, we can now determine the DC power delivered:
Class A: 200 W / 0.25 = 800 W
Class B: 200 ...
This solution calculates the DC input power, heat generation and maximum thermal resistance of class A and B amplifiers. The resulting numbers indicate that a Class A amplifier is an enormous power waster in comparison to a class B amplifier.