Transistors are the fundamental building block of modern electronic devices basically used for controlling, amplifying and generating electrical signals. Transistors comprise of three sections of doped semiconductors. The portion on one side is the emitter and the portion on the opposite side are the collector. The Middle portion is known as the base which forms two junctions between the emitter and the collector.
The Middle portion is known as the base which forms two junctions between the emitter and the collector.
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 characteristics curves are used. However, both the NPN & PNP type bipolar transistors can be made to operate as “ON/OFF” type solid state switch by biasing the transistors base differently to that of a signal amplifier.
Solid state switches are one of the main applications for the use of transistor to switch a DC output “ON” or “OFF”. Some output devices, such as LED’s only require a few milliamps at logic level DC voltages and can therefore be driven directly by the output of a logic gate. However, high power devices such as motors, solenoids or lamps, often require more power than that supplied by an ordinary logic gate so transistor switches are used.
The transistor is also what makes amplifiers work. Instead of having just two states (on or off) it can also be anywhere in between “fully on” and “fully off”.
A small “control current” can then control how big a portion of a bigger “main current” that is going to flow through it. Thereby, the transistor can amplify a signal.
We use transistors in almost all electronics and it’s probably the most important component in electronics.
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