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Analog Electronic Circuits

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Power Amplifier

Question
8 out of 8
 

What is crossover distortion? How it can be minimised?

 

 

The crossover distortion occurs in Class B push-pull amplifier’s output signal as a result of nonlinearity of input characteristics of transistors. Transistors are not turned on at zero applied voltage across the base-emitter junction. When the base-emitter junction is forward biased and it value is greater than cut-in voltage Vγ = 0.3 V for germanium and Vγ = 0.7 V for silicon, transistors turn on. When a sinusoidal base voltage is applied to transistors, the output current is nonsinusoidal. If input voltage < Vγ, the input current is negligible and output current is also neglected and this effect is known as crossover distortion.

 

To minimise the crossover distortion, it is necessary to add a small amount of forward bias to take transistors to the average conduction. Actually, the transistor operates in between Class A and Class B or Class AB.