How can a transistor be used as a 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.

When transistor is used as a switch it operates in which region?

Transistor acts as a switch in the saturation region and cutoff region. The emitter-base junction and the collector-base junction is reverse biased in the cutoff region. Both the junctions are forward biased in the saturation region.

Under what conditions a transistor works as an open switch?

Solution : A transistor will work as an open switch in the cut off state i.e., when both the emitter and collector are reversed biased.

Why are BJTs used?

The main basic function of a BJT is to amplify current it will allow BJTs are used as amplifiers or switches to produce wide applicability in electronic equipment include mobile phones, industrial control, television, and radio transmitters. There are two different types of BJTs are available, they are NPN and PNP.

What is a transistor switch?

A Transistor switch, which is used for opening or closing of a circuit, that means the transistor is commonly used as a switch in the electronic devices only for the low voltage applications because of its low power consumption. Transistor work as a switch when it is in cutoff and saturation regions.

Can transistor work with AC?

Transistor is nothing but a variable resistor. It will work on DC and AC. But the voltage between Base and Emitter (Vbe) must be more that 0.7V. If AC goes below 0.7V or negative the Base to Emitter diode will be reverse biased.

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

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.

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.

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.