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?

(i) Input resistance may be defined as the ratio of small change in the base – emitter voltage() to the resulting change in the base current ( at constant collector- emitter voltage(

Input resistance =

To find the input resistance mark a point P on the characteristics. Now, draw a tangent at point P. The reciprocal of slope of AB will give the input resistance.

(ii) Currant amplification factor r=is defined as the ratio of the change in collector current () to the change in base current ().