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

How does a single pole single throw transistor work?

The transistor operates as a Single Pole Single Throw (SPST) solid state switch. When a zero input signal applied to the base of the transistor, it acts as an open switch.

What are the advantages of a Darlington transistor switch?

As well as its high increased current and voltage switching capabilities, another advantage of a “Darlington Transistor Switch” is in its high switching speeds making them ideal for use in inverter circuits, lighting circuits and DC motor or stepper motor control applications.

Can a bipolar transistor be used as a switch?

Then we can define the “saturation region” or “ON mode” when using a bipolar transistor as a switch as being, both junctions forward biased, V B > 0.7v and I C = Maximum. For a PNP transistor, the Emitter potential must be positive with respect to the Base.

Why is the output at the collector of a 5V transistor zero?

Therefore, as the base current is greater than 56.8 micro ampere current, the transistor will be driven to saturation i.e., it is fully ON, when 5V is applied at the input. Thus, the output at the collector becomes approximately zero.

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 NPN transistor work as a switch?

NPN Transistor as a Switch Based on the voltage applied at the base terminal of a transistor switching operation is performed. 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.

What is the NPN Darlington transistor switch configuration?

The above NPN Darlington transistor switch configuration shows the Collectors of the two transistors connected together with the Emitter of the first transistor connected to the Base terminal of the second transistor therefore, the Emitter current of the first transistor becomes the Base current of the second transistor switching it “ON”.

What is the use of a transistor in a DC motor?

A transistor can also be used to drive and regulate the speed of the DC motor in a unidirectional way by switching the transistor in regular intervals of time as shown in the below figure. As mentioned above, the DC motor is also an inductive load so we have to place a freewheeling diode across it to protect the circuit.

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 BJT 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. Types of BJT Transistors

What is transistor current?

So, the transistor in this condition performs as a switch and the current that flows through the collector is considered as the transistor current. In the same way, when there is no voltage applied at the input terminal, then the transistor functions in the cut-off region and functions as an open circuit.