Question
Draw a circuit diagram of a transistor amplifier in CE configuration.
Define the terms: (i) Input resistance and (ii) Current amplification factor. How are these determined using typical input and output characteristics?Solution
The circuit diagram of a transistor amplifier in CE configuration is given by, 
Input resistance-:
a)The ratio of change in base-emitter voltage to base current gives us the input resistance. We can calculate change in VBE and change in IB from the input characteristics. To find the input resistance, mark a point P on the input characteristic. Draw a tangent at point P. The reciprocal of slope AB will give us the input resistance. 
b) Current amplification factor: It is defined as the ratio of change in collector current to the change in base current. Output characteristics will help to calculate the current amplification factor.
