What is a transistor switch?

What is a transistor switch?

Transistor switches can be used to switch a low voltage DC device (e.g. LED’s) ON or OFF by using a transistor in its saturated or cut-off state When used as an AC signal amplifier, the transistors Base biasing voltage is applied in such a way that it always operates within its “active” region, that is the linear part of the output

What is NPN transistor switching circuit?

Basic NPN Transistor Switching Circuit. The circuit resembles that of the Common Emitter circuit we looked at in the previous tutorials. The difference this time is that to operate the transistor as a switch the transistor needs to be turned either fully “OFF” (cut-off) or fully “ON” (saturated).

What is the power loss in a transistor switch?

When the transistor operating as switch, in the cut off region the current through the transistor is zero and voltage across it is maximum, and in the saturation region the transistor current is maximum and voltage across is zero. Therefore, both the on – state and off – state power loss is zero in the transistor switch.

How does a transistor turn on and off?

With a zero signal applied to the Base of the transistor it turns “OFF” acting like an open switch and zero collector current flows. With a positive signal applied to the Base of the transistor it turns “ON” acting like a closed switch and maximum circuit current flows through the device.

How does a single-pole single-throw transistor work?

For a PNP transistor, the Emitter potential must be positive with respect to the Base. Then the transistor operates as a “single-pole single-throw” (SPST) solid state switch. With a zero signal applied to the Base of the transistor it turns “OFF” acting like an open switch and zero collector current flows.

What is a MOSFET transistor?

MOSFET (metal-oxide-semiconductor field-effect transistor) is the most widely used transistor, also known as the MOS transistor, which was invented by Mohamed Atalla with Dawon Kahng at Bell Labs in 1959. The first truly compact transistor is the MOSFET that could be miniaturized and mass-produced for a wide range of uses.

Why do we use multiple switching transistors in bipolar transistors?

Sometimes the DC current gain of the bipolar transistor is too low to directly switch the load current or voltage, so multiple switching transistors are used. Here, one small input transistor is used to switch “ON” or “OFF” a much larger current handling output transistor.