How does a transistor act as a closed switch?

How does a transistor act as a closed switch?

If a positive signal applied at the input terminal then it acts like a closed 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.

What are transistor switch’s working regions?

Meanwhile, the saturation zone and cut-off area are known as the transistor switch’s working regions. This implies that, by switching between its “top-off” (saturation) and “absolute OFF,” the transistor is used as a switch to basically overwrite its Q-Point and the voltage dividers circuit that is needed for amplification.

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.

Can a PNP transistor be used as a switch?

PNP Transistor Switch We can also use the PNP Transistors as a switch, the difference this time is that the load is connected to ground (0v) and the PNP transistor switches the power to it. To turn the PNP transistor operating as a switch “ON”, the Base terminal is connected to ground or zero volts (LOW) as shown.

Why is a transistor in the saturation region in on condition?

Similarly, in the saturation region, a transistor is biased in such a way that maximum base current is applied that results in maximum collector current and minimum collector-emitter voltage. This causes the depletion layer to become small and to allow maximum current flow through the transistor. Therefore, the transistor is fully in ON condition.

What type of transistors can be used as switches?

Both NPN and PNP transistors can be used as switches. Some of the applications use a power transistor as switching device, at that time it may necessary to use another signal level transistor to drive the high-power transistor.