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How NPN transistor is used as a switch?
NPN Transistor as a Switch When a sufficient voltage (VIN > 0.7 V) is applied between the base and emitter, collector to emitter voltage is approximately equal to 0. Therefore, the transistor acts as a short circuit. The collector current VCC / RC flows through the transistor.
Can a transistor act as a switch?
Transistor switches can be used to switch and control lamps, relays or even motors. When using the bipolar transistor as a switch they must be either “fully-OFF” or “fully-ON”.
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).
What is the saturation region of a PNP transistor?
Therefore the transistor is switched “Fully-ON”. Then we can define the “saturation region” or “ON mode” when using a bipolar transistor as a switch as being, both junctions forward biased, VB > 0.7v and IC = Maximum. For a PNP transistor, the Emitter potential must be positive with respect to the Base.
How does a Darlington transistor work as a switch?
Darlington Transistors simply contain two individual bipolar NPN or PNP type transistors connected together so that the current gain of the first transistor is multiplied with that of the current gain of the second transistor to produce a device which acts like a single transistor with a very high current gain for a much smaller Base current.
Which is part of a transistor is fully switched on?
Current flows freely from collector to emitter with almost zero resistance. In this mode, the transistor is fully switched ON and is essentially a close circuit. Saturation Region is also primarily used in switching and digital logic circuits.