Transistor - Characteristics

Description:

Forward/Input characteristic

It is a graph of input current versus input voltage.

In N-P-N common emitter configuration, it is a graph of base current (I_B) versus voltage between base and emitter i.e. base voltage (V_BE), when output voltage (V_CE) is kept constant.

To study input characteristic V_CE is kept constant, V_BE is increased in small steps and I_B is recorded at every step.

When we plot I_B verses V_BE we get input characteristic as –

Reverse/Output Characteristic

It is a graph of output current versus output voltage.

In N-P-N common emitter configuration, it is a graph of collector current (I_C) versus voltage between collector and emitter i.e. collector voltage (V_CE), for the fixed value of the base current.

To study output characteristics, I_B is kept constant. V_CE is increased in small steps and I_C is recorded at every step.

When I_C versus V_CE is plotted we get output characteristics as -

The output resistance in this mode varies from few kΩ to 100kΩ

Total current of emitter is given by –

I_E = I_B + I_C