POWER TRANSISTOR

• Power amplifiers are used to provide power required to drive an current operated load.

• This load maybe loud speaker in an audio circuit, a horizontal deflection yoke in a video circuit, a magnetic core in a computer memory circuit or a servo motor in an industrial control circuit.

• These amplifiers operate with large input signals. In a power amplifier, the increased power must come from the D.C power source supplying the active device used in the circuit. Power transistors are used an active devices.

• Active device in power amplifier, circuit is to reproduce in the output circuit a large power signal that is a replica of the relatively small signal applied to its input circuit, differing only in the amplitude of power

• Power amplifier circuits are used in both A.F. and R.F. circuits.

• In power amplifier circuits, the active devices may be operated as class A, class All, class B or class C. Although all classes of operation may he used in both R.F. and AT. Power amplifier circuits. Class C is used primarily in R.F. amplifiers, due to its higher efficiency

• Depending upon amount of power output required, the active devices used in power amplifiers may be operated as (1) in single (2) in parallel (3) in push pull.