Ex.No.

CHARACTERISTICS OF BJT IN CE CONFIGURATION

AIM: To study and plot the transistor characteristics in CE configuration.

APPARATUS REQUIRED:
Transistor Kit,Ammeter, Voltmeter,
Resistor, Connecting Wires.

THEORY:
A BJT is a three terminal two – junction semiconductor device in which the
conduction is due to both the charge carrier. Hence it is a bipolar device and it
amplifier the sine waveform as they are transferred from input to output. BJT is
classified into two types – NPN or PNP. A NPN transistor consists of two N types
in between which a layer of P is sandwiched. The transistor consists of three
terminal emitter, collector and base. The emitter layer is the source of the charge
carriers and it is heartily doped with a moderate cross sectional area. The
collector collects the charge carries and hence moderate doping and large cross
sectional area. The base region acts a path for the movement of the
charge carriers. In order to reduce the recombination of holes and electrons the
base region is lightly doped and is of hollow cross sectional area. Normally the
transistor operates with the EB junction forward biased.

In transistor, the current is same in both junctions, which indicates that

there is a transfer of resistance between the two junctions. Hence known as
transfer resistance of transistor.

PROCEDURE:

INPUT CHARECTERISTICS:

1. Connect the circuit as per the circuit diagram.

2. Set VCE , vary VBE in regular interval of steps and note down the
Corresponding B reading. Repeat the above procedure for different
values of VCE.
3. Plot the graph: VBE Vs IB for a constant VCE.

OUTPUT CHARACTERISTICS:

1. Connect the circuit as per the circuit diagram.

2. Set IB, Vary VCE in regular interval of steps and note down the
corresponding IC reading. Repeat the above procedure for different values
of IB.
3. Plot the graph: VCE Vs IC for a constant IB.
 CIRCUIT DIAGRAM:
(0 – 30)mA
1 KΩ
- +
A

(0 – 250) μA C
+ +
10 KΩ + - (0-30)V
A BC107 V (0-30)V -
+ + B
(0-30)V (0-1)V V E -
- -

MODEL GRAPH:
INPUT CHARACTERISTICS: OUTPUT CHARACTERISTICS:

µA
mA

IB I
C
VCE = 0V
VCE = 5V
IB=60μA

IB=40μA

IB=20μA

0
VBE(V) 0
VCE(V)
TABULAR COLUMN:
INPUT CHARACTERISTICS:

VCE=1V VCE=2V
VBE(V) IB(μA) VBE(V) IB(μA)

OUTPUT CHARACTERISTICS:

IB=20μA IB=40μA
VCE(V) IC(mA) VCE(V) IC(mA)

RESULT:
The transistor characteristics of a Common Emitter (CE)
configuration were plotted
Ex.No:6

CHARACTERISTICS OF BJT IN CB CONFIGURATION

AIM: To study and plot the transistor characteristics in CB configuration.

APPARATUS REQUIRED:
Transistor Kit, Ammeter, Voltmeter,
Resistor, Connecting Wires.

THEORY:

In this configuration the base is made common to both the input and out. The emitter
is given the input and the output is taken across the collector. The current gain of
this configuration is less than unity. The voltage gain of CB configuration is high. Due
to the high voltage gain, the power gain is also high. In CB configuration, Base is
common to both input and output. In CB configuration the input characteristics relate

IE and VEB for a constant VCB. Initially let VCB = 0 then the input junction is
equivalent to a forward biased diode and the characteristics resembles that of a
diode. Where VCB = +VI (volts) due to early effect IE increases and so the

characteristics shifts to the left. The output characteristics relate IC and VCB for a

constant IE. Initially IC increases and then it levels for a value IC = αIE. When IE is

increased IC also increases proportionality. Though increase in

VCB causes an increase in α, since α is a fraction, it is negligible and so I C

remains a constant for all values of VCB once it levels off.

PROCEDURE:
INPUT CHARACTERISTICS:
It is the curve between emitter current IE and emitter-base voltage VBE
at constant collector-base voltage VCB.
1. Connect the circuit as per the circuit diagram.
2. Set VCE=5V, vary VBE in steps of 0.1V and note down the
corresponding IB. Repeat the above procedure for 10V, 15V.
3. Plot the graph VBE Vs IB for a constant VCE.
4. Find the h parameters.

OUTPUT CHARACTERISTICS:
It is the curve between collector current IC and collector-base voltage VCB
at constant emitter current IE.
1. Connect the circuit as per the circuit diagram.
2. Set IB=20μA, vary VCE in steps of 1V and note down the corresponding IC.

Repeat the above procedure for 40μA, 80μA, etc.

3. Plot the graph VCE Vs IC for a constant IB.
4. Find the h parameters

RESULT:
The transistor characteristics of a Common Base (CB) configuration were
plotted and studied.
CIRCUIT DIAGRAM:
(0-1)mA (0-30)mA

+ - + -
10 KΩ 1KΩ -
+ + +
(0-30)V VEB (0-2)V (0-30)V (0-30)V
- - -
TABULAR COLUMN:
INPUT CHARACTERISTICS:

S.No. VCB = V VCB = V VCB = V

VEB IE VEB IE VEB IE

(V) (μA) (V) (μA) (V) (μA)

OUTPUT CHARACTERISTICS:

S.No. IE= mA IE= mA IE= mA

VCB Ic VCB Ic VCB Ic

(V) (mA) (V) (mA) (V) (mA)
MODEL GRAPH:
INPUT CHARACTERISTICS:

IC
(mA)
VCB1
IE2
VCB2

IE1 VEB1 VEB2 VEB (V)

OUTPUT CHARACTERISTICS:

IC
(mA) IE3

IC2 IE2
IC1
IE1

VCB1 VCB2 VCB (V)