What are the areas of operation of a transistor switch?
The areas of operation for a transistor switch are known as the Saturation Region and the Cut-off Region.
How is a bipolar transistor used as a switch?
If the circuit uses the Bipolar Transistor as a switch, then the transistor’s biasing, whether NPN or PNP, is designed to operate the transistor on both sides of the previously seen “I-V” characteristic curves. The transistor switch operating areas are referred to as the Saturation Region and the Cut-off Area.
What’s the difference between a transistor and a NPN switch?
The equations for calculating the Base resistance, Collector current and voltages are exactly the same as for the previous NPN transistor switch. The difference this time is that we are switching power with a PNP transistor (sourcing current) instead of switching ground with an NPN transistor (sinking current).
When does the gain formula for a transistor no longer apply?
In other words, once a transistor switch reaches the saturation point, the gain formula I C = Beta x I B no longer applies because the voltage drop across the collector/emitter terminals (V CE (sat)) has reached its lowest saturation voltage of .1V.
Why are transistor switches used in logic gates?
However, high power devices such as motors, solenoids or lamps, often require more power than that supplied by an ordinary logic gate so transistor switches are used.
Can a transistor be used as a solid state switch?
A transistor can be used as a solid state switch. If the transistor is operated in the saturation region then it acts as closed switch and when it is operated in the cut off region then it behaves as an open switch. The transistor operates as a Single Pole Single Throw (SPST) solid state switch.