Semi-conductor Devices and Electronics
11.0 Transistor
11.0 Transistor
The transistor was invented in 1948 by John Bardeen, Walter Brattain and William Shockley at Bell Laboratory in America.
A transistor is basically a silicon or germanium crystal containing three separate regions
A transistor has two $p-n$ junctions, so it is known as Bipolar Junction Transistor (BJT).
One junction is between the emitter and the base, and is called the emitter-base junction or emitter junction.
The other junction is between the base and the collector, and is called collector-base junction or collector junction.
Types of transistor
- $n-p-n$ transistor
- $p-n-p$ transistor
These types of transistors has three segments namely base, emitter and collector.
Base: This is the central segment. It is very thin and lightly doped.
Emitter: This is the segment on one side of the transistor as shown in the figure. It is of moderate size and heavily doped. The function of emitter is to emit or inject electron in case of a $n-p-n$ type transistor and emit or inject electron in case of a $p-n-p$ type transistor.
Collector: This segment collects electrons in case of $n-p-n$ type transistor and holes in case of a $p-n-p$ type transistor from the base. The collector side is moderately doped and larger in size as compared to the emitter since it is required to dissipate more heat.
11.0.1 $n-p-n$ transistor
In this type of transistor, the two segments of $n$-type semiconductor (emitter and collector) are separated by a segment of $p$-type semiconductor (base).
$n-p-n$ transistors are represented as shown in the figure.
11.0.2 $p-n-p$ transistor
In this type of transistor, the two segments of $p$-type semiconductor (emitter and collector) are separated by a segment of $n$-type semiconductor (base).
$p-n-p$ transistors are represented as shown in the figure.
