Classes of Bipolar Junction Transistor

Classes of Bipolar Junction Transistor

1. Class-A: Transistor operate in active region at all times i.e. collector current flows for 360º of the ac cycle.
   • The maximum efficiency of class A amplifier is 25%.
   • It has very less distortion.
   • Used in low power amplifier.
2. Class-B: Collector current flows for only half the cycle 180º. This is why transistor transistor Q-Point lies at cut off.
   • The maximum efficiency of class B amplifier is 78.5% with Push-Pull arrangement.
   • It has small to moderate distortion.
   • Used as power amplifier.
   • Uses push-pull effect and complementary output transistors.
3. Class-C: In this operation Collector current flows for less than 180º of the ac cycle.
• The maximum efficiency of class C amplifier is near to 100%.
• It has large distortion.
• Used in Tuned RF Power amplifier and final amplifier stages in communication circuits.

Reference:

Albert Malvino and David J Bates, “Electronic Principles”, 7th Edition, TATA McGRAW HILL.