VOLTAGE AND POWER AMPLIFIERS

VOLTAGE AMPLIFIER:
The transistor with high β is used in the circuit. In other words, those transistor are employed which have thin base. 
The input resistance Rin of a transistor is sought to be quite low as compared to the collector load Rc. 
Relatively high load Rc is used in the collector.
To permit this condition, voltage amplifiers are always operated at low collector current.
If the collector current is small, we can use large Rc in the collector circuit.
POWER AMPLIFIER 
A power amplifier is required to deliver a large amount of power and as such it has to handle large current. 
The size of power transistor is made considerably larger in order to dissipate the heat produced in the transistor during operation. 
The base is made thicker to handle larger current