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How BJT can work as a switch?
The three terminals of BJT are base, emitter and collector. BJT is either a PNP transistor or NPN transistor based on the doping type of the three terminals. The transistor acts as a switch in the cut-off mode and the saturation mode. The transistor is fully off in the cutoff region and fully on the saturation region.
Can we use transistor as 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”.
How does transistor works as a switch?
One of the most common uses for transistors in an electronic circuit is as simple switches. In short, a transistor conducts current across the collector-emitter path only when a voltage is applied to the base. When no base voltage is present, the switch is off. When base voltage is present, the switch is on.
Why do you use a BJT as a switch?
There are plenty of reasons why you would use a BJT or a transistor as a switch. But for me, I think the main reason is driving a load with higher current consumption or voltage. For example, your load requires 100mA but you can only draw 20mA from your source, which is common for a GPIO pin of a microcontroller.
What’s the difference between a PNP and NPN transistor?
To keep a straight emitter notation, the arrow in a schematic is always the emitter. The PNP’s emitter is “emitting” electrons and the NPN’s emitter is “emitting” holes. The PNP is distinguished from the NPN transistor by the direction of the arrow on the emitter.
Can a transistor be used as a positive ground switch?
It is also possible to use an NPN transistor if a positive ground configuration is needed. The basic NPN transistor switching circuit is similar to the Common Emitter circuit with the difference of turning the transistor fully OFF or fully ON.
Which is the best transistor switch to use?
The PNP variety is the cost commonly used transistor switch as shown below. Getting the transistor in a saturation state is the secret to making a transistor switch work properly. To guarantee our transistor switch is always saturated, it is best to calculate about 30% more current than we will need in actual practice.