COMMON COLLECTOR CONNECTION
In this configuration the input is applied between the base and the collector and the output is taken from the collector and the emitter. Here the collector is common to both the input and the output circuits as shown in Fig.
Common Collector Transistor Circuit
In common collector configuration the input current is the base current IB and the output current is the emitter current IE. The ratio of change in emitter current to the change in the base current is called current amplification factor.
It is represented by
COMMON COLLECTOR CIRCUIT
A test circuit for determining the static characteristic of an NPN transistor is shown in Fig. In this circuit the collector is common to both the input and the output circuits. To measure the base and the emitter currents, milli ammeters are connected in series with the base and the emitter circuits. Voltmeters are connected across the input and the output circuits to measure VCE and VCB
Common Collector Input Characteristic Curve
- It is a curve which shows the relationship between the base current, IB and the collector base voltage VCB at constant VCE This method of determining the characteristic is as follows.
- First, a suitable voltage is applied between the emitter and the collector. Nextthe input voltage VCB is increased in a number of steps and corresponding values of IE are noted.
- The base current is taken on the y-axis, and the input voltage is taken on the x-axis. Fig. shows the family of the input characteristic at different collector- emitter voltages.
- The following points may be noted from the family of characteristic curves. 1.Its characteristic is quite different from those of common base andcommon emitter circuits.
- It is a curve which shows the relationship between the emitter current l and collector-emitter voltage, the method of determining the output characteristic is as follows.
- First, by adjusting the input a suitable current IB is maintained. Next VCB increased in a number of steps from zero and corresponding values of IE are noted.
- The above whole procedure is repeated for different values of IB. The emitter current is taken on the Y-axis and the collector-emitter voltage is taken on the X-axis.
- Fig shows the family of output characteristics at different base current values. The following points are noted from the family of characteristic curves.
1.This characteristic is practically identical to that of the common emitter circuit.
2.Its current gain characteristic for different values of VCE is also similar to that of a common emitter circuit.