Question

Draw the circuit arrangement for studying the input and output characteristics of n-p-n transistor in CE configuration. 

Draw the typical nature of these input and output characteristics. Explain how these are obtained. 

Define the terms (i) input resistance and (ii) current amplification factor

Answer 1

Input characteristics: The variation of the base current I_b with the base-emitter voltage V_be at constant V_ce. Input characteristics can be drawn, when the transistor is in active state, so V_ce is kept enough large. So base collector junction remain in reverse biased mode i.e., V_ce >> 0.7V. 

Output characteristics: Output characteristic is obtained by measuring the collector current I_C with the variation in V_ce keeping base current Ib constant. Input resistance: It is defined as the ratio of change in base - emitter voltage V_be to the resulting change in base current Ib at constant V_ce.

Current Amplification: It is defined as the ratio of change in collector current I_C to the change in base current Ib at a constant V_ce, when the transistor is in active state.

β_ac = (ΔI_c/ΔI_b)