Bipolar Transistor and its configurations

School of Basic and Applied Sciences(CAT-3 B Tech Sem-I 2020-21)
Course Code : BEE01T1003 Name: Basic Electrical and Electronics Engineering
Program Name:B.Tech
Topic: COMMON BASE, COMMON COLLECTOR,COMMON EMITTER
CONFIGURATIONS AND CHARARACTERISTICS
Section- 8
Enrolment Number &Name of Student
(1) 20SCSE1010229 - Avtar Singh
(2) 20SCSE1010416 - Syed Ali Asdaque

Program Name: B.Tech (CSE)
Bipolar Transistor
Bipolar Transistors are current regulating
devices that control the amount of current
flowing through them from the Emitter to
the Collector terminals in proportion to the
amount of biasing voltage applied to their
base terminal.
There are two basic types of bipolar
transistor construction, PNP and NPN

Bipolar Transistor construction
The Bipolar Transistor basic construction
consists of two PN-junctions producing three
connecting terminals with each terminal
being given a name to identify it from the
other two. These three terminals are known
and labelled as the Emitter ( E ), the Base ( B
) and the Collector ( C ) respectively.

Bipolar Transistor construction
The principle of operation of the two
transistor types PNP and NPN, is exactly
the same the only difference being in their
biasing and the polarity of the power
supply for each type.
The direction of the arrow always points
from the positive P-type region to the
negative N-type region for both transistor
types

Bipolar Transistor Configurations
As the Bipolar Transistor is a
three-terminal device, there are
basically three possible ways to
connect it within an electronic
circuit with one terminal being
common to both the input and
output
Common Base Configuration – has Voltage Gain but no
Current Gain.
Common Emitter Configuration – has both Current and
Voltage Gain.
Common Collector Configuration – has Current Gain but no
Voltage Gain.

The Common Base (CB) Configuration
In Common Base or grounded base configuration,
the base connection is common to both the input
signal and the output signal.
The input signal is applied between the
transistors base and the emitter terminals,
while the corresponding output signal is taken
from between the base and the collector
terminals

Bipolar transistor configuration has a high ratio of output to
input resistance or more importantly “load” resistance ( RL ) to
“input” resistance ( Rin ) giving it a value of “Resistance Gain”.
voltage gain ( Av ) for a common base configuration:
Ic/Ie is the current gain (alpha ( α )) and RL/Rin is the resistance gain.

The Common Emitter (CE)
Configuration
In Common Emitter or grounded emitter
configuration, the input signal is applied between
the base and the emitter, while the output is
taken from between the collector and the
emitter.
This type of configuration is the most used
circuit for transistor-based amplifiers, and which
represents the “normal” method of bipolar
transistor connection.

The current flowing out of the transistor must be
equal to the currents flowing into the transistor as
the emitter current is given as Ie = Ic + Ib.
As the load resistance ( RL ) is connected in
series with the collector, the current gain of the
common emitter transistor configuration is quite
large as it is the ratio of Ic/Ib.
Where: “Ic” is the current flowing into the collector
terminal,“Ib” is the current flowing into the base
terminal and “Ie” is the current flowing out of the
emitter terminal.

The Common Collector (CC) Configuration
In the Common Collector or grounded collector configuration, the
collector is connected to ground through the supply.
The collector terminal is common to both the input and the output.
The input signal is connected directly to the base terminal, while
the output signal is taken from across the emitter load resistor.
The common collector, or emitter follower configuration is very
useful for impedance matching applications because of its very
high input impedance, in the region of hundreds of thousands of
Ohms while having a relatively low output impedance

In the common collector configuration, the
load resistance is connected in series with the
emitter terminal, so its current is equal to that
of the emitter current.
The load resistance in this type of transistor
configuration also has both the collector
current and the input current of the base
flowing through it

Bipolar Transistor Configurations

Characteristics of the Transistor Configurations

Bipolar Transistor and its configurations

Bipolar Transistor and its configurations

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