Question

Define the terms : Input resistance How are these determined using typical input and output characteristics?

Answer 1

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

Input resistance, `R_i=(DeltaV_(BE))/(DeltaI_B)`

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