Transistor as an amplifier with example
Transistor as an amplifier:
Transistors are often used as amplifiers to increase input signal in radios, televisions and some other applications .The circuit may be designed to increase the current or voltage level.
The power gain is the product of current gain and voltage gain (P=V*I).
Amplifier example:
As you see, the transistor is biased to be always on. The input signal is amplified by this circuit. The frequency of output is the same as its input, but the polarity of the signal is inverted.
With Q1 properly biased, direct current flows continuously, with or without an input signal, throughout the entire circuit
It is introduced into the circuit by the coupling capacitor and is applied between the base and emitter.
As the input signal goes positive, the voltage across the emitter-base junction becomes more positive.
This in effect increases forward bias, which causes base current to increase at the same rate as that of the input sine wave.
Modes of transistor operation
Common - base
Common - emitter
Common - collector
Particular terminal is common to both input and output