15-11-2017, 04:14 PM
A transistor works in the active region when it worked as an amplifier. When a transistor works like a switch, it works in the regions of cut and saturation. In the Cutting State, both the base junctions of the emitter and the collector base are biased in the opposite direction. But in the saturation region both unions are biased forward. Switch is a very useful and important application of transistors. In most digital ICs, transistors will function as a switch to reduce power consumption. It is also a very useful circuit for an electronics enthusiast, since it can be used as a controller, inverter, etc...
Circuit diagram - Transistor as a switch
From the previous circuit we can see that the control input Vin is given to the base through a current limiting resistor Rb and Rc is the collector resistance that limits the current through the transistor. In most cases, the output is taken from the collector, but in some cases the load is connected in the Rc location.
• ON = Saturation
• OFF = Cutoff