M G Mahesh Assistant Prof ESSOR EEE Dept

M. G. Mahesh Assistant Prof. ESSOR EEE Dept AITS RAJAMPET

INTRODUCTION �There are three types of configurations in which Transistor operation is carried out namely CB, CE, CC. �CC : In this circuit the base terminal of the transistor serves as the input, the emitter is the output, and the collector is common to both �Signal input between base and common collector. �Signal output between emitter and common collector. �The CC circuit is also known as an emitter follower since the output voltage at the emitter follows the input voltage at the base. �It has voltage gain slightly less than unity.

SIMPLE CIRCUITDIAGRAM Input is applied to base and collector. Output is from emitter-collector circuit.

WORKING : INPUT CHARACTERISTICS �The CC input characteristics are quite different from CB & CE characteristics. �This is because input voltage VBC is largely determined by output voltage VEC �VEB =VEC-VBC As VBC increases with VEC constant VEB decreases hence IB decreases INPUT CHARACTERISTIC

OUTPUT CHARACTERISTICS �Here VCE increases IE also increases. �Just as in common emitter output characteristics IC increases with increasing IB , so IE also increases here with increasing IB �Hence for constant VEC, IE increases with IB

APPLICATION �It is useful as an impedance matching device since its input impedance is much higher than its output impedance. It is also termed a “buffer" for this reason and is used in digital circuits with basic gates. �When the voltage divider used but it is a poor voltage source because it is so strongly affected by the value of the load resistor. The same voltage divider with the transistor buffer will supply power to keep the voltage constant over its range of operation. �It is also used for cascade amplifier.