UNIT 1-TRANSISTORS
A transistor is a semiconductor
device used to amplify or switch
electronic signals and electrical
power. It is composed of
semiconductor material with at
least three terminals for connection
to an external circuit.
Type Of Transistor:
The most common type of transistor is called bipolar junction
transistor and these are divided into two types.
They Are:
i) n-p-n transistor :
#Base is energized to allow current flow
ii) p-n-p transistor
#Base is connected to a
lower potential to allow current flow
n-p-n BJT Transistors
1. High potential at
collector
2. Low potential at
emitter
3. Allows current flow
when the base is given a
high potential
p-n-p BJT Transistors
1. High potential at
emitter
2. Low potential at
collector
3. Allows current flow
when base is connected
to a low potential
A transistor has three regions namely,
1. Emitter
2. Base
3. Collector
Emitter:
The section on one side that supplies charge carriers (electron or holes) is
called the emitter. The emitter is always forward biased w.r.t. base so that it
can supply a large number of majority carriers.
Collector:
The section on one side that collects charges is called the
collector. The collector is always reverse biased w.r.t. base.
Its function is to remove charges from its junction with
the base.
Base:
The middle section which forms two pn junctions between the emitter
and the collector is called the base. The base-emitter junction is forward
biased, allowing low resistance for the emitter circuit. The base-collector
junction is reverse biased and provides high resistance in the collector
circuit
