Transistor: Common Collector Configuration (or) Characteristics of a Common Collector

COMMON COLLECTOR CONFIGURATION (OR) CHARACTERISTICS OF A COMMON COLLECTOR

Figure shows the circuit diagram of common-collector configuration. In this case, collector terminal is common to both the input and output circuit.

Input Characteristics of Common-Collector Configuration

At a constant collector to emitter voltage (V_CE). The plot draw between the base current (I_B) to collector to base voltage (V_CB). It is shown in fig.3.51.

Its characteristics are quite different from either common base or common emitter input characteristics. This difference is due to the fact that the input voltage V_CB is largely determined by the level of collector to emitter voltage V_CE.

Output Characteristics of Common Collector Configuration

It is curve between emitter current I_E and collector to emitter voltage V_CE constant base current I_B. It is shown in fig.3.52.

I_C is approximately equal to I_E the common collector output characteristics are similar to common emitter output characteristics.

The current gain in the common collector configuration. Base current I_B is the input current and emitter current I_E is the output current.

I_E = I_B + I_C

I_E = I_B + βI_B

I_E = (1+ β) I_B

I_E / I_B = (Hβ)