What are alpha, beta and gamma of transistors?

 Alpha, beta and gamma in case of transistors indicate the current gain in different configurations. Alpha is the current gain in common base configuration. It is the ratio of collector current to emitter current. Alpha is always less than 1. In common base configuration, emitter is the input terminal and collector the output terminal while base is the common terminal. This configuration is also known as grounded base configuration. When there is no AC input, the alpha is known as DC Alpha. Alpha can be increased by making the base thin and lightly doped. 



Beta is the current gain in common emitter circuit. It is the ratio of collector current to base current. Beta is always more than 1. This configuration is also called grounded emitter configuration. Base is the input terminal and collector the output terminal. Gamma is the current gain in common collector circuit. Base is the input terminal in this configuration, also known as grounded collector configuration. Here output terminal is the emitter. Though a transistor is a three terminal device, we need two terminals for input and two for output. That is why one terminal becomes common to input and output in the configurations mentioned above. The common terminal is grounded. 


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