The transistor can be used as a switch or as an amplifier by forward/reverse biasing the emitter to base and base to collector junctions. Based on biasing, the transistor can be operated in the cut-off, active, and saturation regions of the transfer characteristics of the transistor. In this post, we will discuss the operation of BJT in active, saturation, and cutoff regions.
TRANSISTOR AS A SWITCH :
CUT OFF REGION:
In the cut-off region, the emitter-to-base and base-to-collector junction is in the reverse bias, and no current flows through the transistor. The transistor acts as an open switch. In the saturation region, both the junctions are in forwarding bias, and the transistor acts as a closed switch.
In the off region, the output of the transistor VCE, IC, IB, and IE=0
SATURATION REGION:
In the saturation region, the B-E and B-C junctions are forward-biased, and IC=IE
ACTIVE REGION:
TRANSISTOR AS AN AMPLIFIER:
In the active region, the emitter to the base junction is forward-biased, and the base-to-collector junction is reverse-biased. In the active region, the transistor acts as an amplifier. In the active state, the collector current is β times the base current, i.e.,
Where,
Ic = Collector current
Ib= Base Current
β = Current gain
Really interested.
Very Helpful
this has really given a good insight, thanks……