As mentioned in the previous chapter, transistor is a device which is used to amplify and switch electrical signals and power.
In this module, we will learn a brief introduction that how a transistor work as switch and amplifier.Also, we will make a practical circuit connection of transistor as a switch & transistor as amplifier.
Transistor as switch
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.
The transistor will be in only one of two states: off or on. The transistor is off when there is no voltage is applied to the base and the switch is on when the voltage is applied to the base so that the current can flow through collector without restriction.
SW 1 -> This switch controls whether current is allowed to flowing to the base. Closing this switch turns on the transistor, which causes current to flow through the LED. Thus, closing this switch turns on the LED even though the switch isn’t placed directly within the LED circuit.
Load-> This is the 5 mm Led
You might be wondering why you’d need to use transistor as switch , we can simply use a switch in this circuit. Of course you could, but that would defeat the principle that this circuit that a transistor allows you to use a small current to control a much larger one.
Transistor as amplifier
A transistor acts as an amplifier by raising the strength of a weak signal. The DC bias voltage applied to the emitter base junction, makes it remain in forward biased condition. Thus a small input voltage results in a large output voltage, which shows that the transistor works as an amplifier.
