EXPERIMENT N0-3

AIM OF THE EXPERIMENT:

Design and analysis of Audio frequency signal amplifier using transistor.

Equipment required
1. Cathode Ray Oscilloscope
2. Function generator
3. Trainer kit with
power supplyy

Components requiredd:
SI. No Name Specification
NPN Bipolar Junction transistor BC108
Resistor 56KQ-1pc, 10K0-1pc,4.7KQ-1pc,
|KO-1pc
Capacitor 33uF-2pc, 10uF-lpc
CIRCUIT DIAGRAM:
12T
Re
6 k R 347k2
Gain
(dB)
10uF

Funchon 33 uF
CRo I-30B
R2 C
10 k 1 T i s
&W--
Frequency
- GNO (Hz)
Figure.3.1 Single stage BJT amplifier Figure.3.2 Frequency response
THEORY: -

In a single stage amplifier the transistor is biased at active region by the resistors R1 & R, known as biasing
resistor, Re is the collector resistor protects the transistor against accidental short circuit across the emitter resistor,
Re&large input voltage swing, and Re provides stability to the circuit. The coupling capacitor Ce blocks any DC
signals from the biasing circuit of the transistor to the load and also blocks any DC signal from the function
generator to the transistor. Hence, it provides the stability of the Q point of the transistor as per the biasing circuit.
The emitter bypass capacitor, CE improves the gain of the amplifier at the high-frequency. From above discussion
we found that AC signal from the Audio generator gets in to the amplifier circuit and the amplified AC signal
delivers to the output load without disturbing Q' point of the transistor. But, these Ce & CE decrease the gain at
low frequency and the gain also decreases at high frequency as hfe decreases at high frequency. Hence, the range
of the frequencies over which the gain remains constant is called the bandwidth (BW)and the transistor should
be operated as an amplifier in that range. For geting the BW, we are going for -3dB from mid-band gain

PROCRDURE:
1. Construct the audio signal amplifier circuit in trainer kit as per the diagram shown in Figure-3.1
2. Connect function generator for supplying input signal.
3. In function generator, select sinewave with 20mV peak to peak and IKHz frequency.
4. Connect oscilloscope at the output as shown in figure.
 factor for different input signal amplitude
5. Observe the output signal on the oscilloscope and calculate the amplification
(listed in Table-1). Note: student need to take tracing of input and output signal for any one value of input.
in Table-2.
6. Now, set the input signal to 20mV peak to peak and observe the output for
different input frequency as listed

TABULATIONS:

Table-1:

Serial no | Input signal amplitude Vin Output signal Gain=Voud Vn

/ (peak to peak) amplitude Vout
(peak to pealk)_
20mV
30mV
40mV

Table-2: Frequency response of Amplifier (Input voltage is fixed to 20mVolt peak to peak).

Serial Frequency Output Voltage Gain-Vout/Vin Gain in

no Vout dB-201og(Vout/Vin)
(peak to peak)
100Hz
50OHz
IKHz
SkHz
10KHz
50KHz
100KHz
8 300KHz

FREQUENCY RESPONSE GRAPH: To be plotted on a semilog graph paper

Calculation: To be shown on graph paper and record. Refer to Figure-3.2. After plotting frequency response graph,
draw a line -3dB down to peak gain as shown in Fig.3.2. Thedifference between two intersection point in X axis (frequency
axis) is called 3dB bandwidth of the amplifier where gain of the amplifier is almost constant.

CONCLUSION: (To be written by students after the experimen)

 EXPERIMENT NO-4
Design of voltage amplifier with
user
AIM OF THE EXPERIMENT:
defined gain using Operational amplifier (OPAMP)
EQUIPMENT REQUIRED: The components and equipment requiredd
for this experiment are:
1. Op-amp (LM 741)
2. CRO with probes
3. Function Generator
4.Resistors(10K)
5. Universal Trainer kit/Breadboard

Theory, Pin configuration and Circuit Diagram:

An Operational Amplifier, or op-amp for short, is fundamentally a

voltage amplifying device designed to be used with external

feedback components such as resistors and capacitors between its
output and input terminals. These feedback components determine
the resulting function or "operation" of the amplifier and by virtue of
the different feedback configurations whether resistive, capacitive or
both, the amplifier can perform a variety of different operations,
giving rise to its name of "Operational Amplifier".
In this experiment, IC741 general purpose OP AMP will be used to
design a voltage amplifier.
The 741 Op Amp IC is a monolithic integrated circuit, consisting of a
general purpose Operational Amplifier. It was first manufactured by
Fairchild semiconductors in 1963. The number 741 indicates that
his operational amplifier IC has 7 functional pins, 4 pins capable of
taking input and 1 output pin.

IC 741 Op Amp can provide high voltage gain and can be operated
over a wide range of voltages, which makes it the best choice for
use in integrator, Summinng amplifiers and general feedback
applications. It also features short circuit protection and internal
frequency compensation circuits built in it.

Isic Electronics Engineering Laboratory/School of Electronics Engineering/KIIT/Manual Version-1.1

 741 OPAMP:
Pin Configuration of

N/C
Offset Null (-) L
V+
inverting Input
Out
Non-Inverting Input
Offset Null (+)
v.
5

or
OPAMP be configured as an inverting
can
CIRCUIT DIAGRAM:
nature of output will change depending
non-inverting amplifier. The
mode. Inverting mode offers a phase shift of 180'
upon its operating
no phase shift takes place
whereas in case of non-inverting mode,
be varied by changing the value of
The gain of the amplifier can

resistance RA, RB or both. Generally,

it is preferred to vary
to set it to user-defined
feedback resistance RB to vary the gain and
value. Circuit diagrams of Inverting and Non-inverting
amplifieer
circuit is shown below:
 2
a) Inverting Amplifier
12

Rg= 20 ka

10 kO
RA =

w- 2 LM741
Vour- V
V.( sine
1 kHz
vP

nverting amplifier) , aVo

Fig.1 (Circuit dingran of

b) Non-Inverting Amplifier:

Rp =
20 kO

RA 10 ka

LMT41
yVout (1+v,
V sine
1 kHz

Fig.2(Circuit dingram of Non-Inverting amplifier)

 other is non-
and
is
inverting
applied to the
one is
terminals, input
amplifier input
lnput is
has two input amplifiers
amplifier
Op-amp n o n - i n v e r t i n g

t e r m i n a l . In
nIn non
non
inverting
inverting and in op-amp.

input
terminal
of the but in
non-inverting
terminal
signal
signal
the inverting
input with input of input
applied to output is inphase
out of
phase
amplifiers phase or
inverting is 180°
amplifier output resistors are
Inverting
Ra & Rs
signal. configuration element.
In close loop is the feedback
element and RB inverting input
used where Ra
is the input applied to the
is
amplifier, the input g r o u n d e d . For non-inverting Fornon-inverting

For an inverting is
non-inverting input to the
non-inverting
via RA & directly
amplifiers the input
signal is applied Voltage gain
for non-
resistor RA is grounded.
amplifiers is:
input, while the input for inverting
is (1+ RB/RA) and will always be
inverting amplifiers voltage gain
amplifiers
(-RE/RA). For non-inverting
greater than

of Inverting
OBSERVED WAVEFORM: Input & output waveforms
circuits are shown below:
and Non-inverting amplifier

Inverting Amplifier:
Output Waveformn
Input Waveform
t ulpuh

Vm4

-Vms
Fig.3 (Output wavefom of ivetng ainplifien)
Non-Inverting Amplifier:
Vm Output Waveform

Vwn
Input Waveform

Fig4 (Output wavefom of Non-Inverting ampliífe)

6. PROCEDURE:

The procedure to design and analyze the circuit in hardware is given

below:

1. Connect the circuit as per the circuit diagram.

2. To display input, connect Function Generator at CH-1 of CRO and
generate 1 volt peak to peak sine wave form.
3. Connect +12V(or +15V) at Pin-7 and -12V (or -15V) at Pin-4 of
741 1C.
4. Connect the input to the inverting input terminal (Pin-2) via RA
for inverting amplifier and non-inverting input terminal (Pin-3) for
non-inverting amp.
5. To display output, connect the CRO (CH-2) across the output
terminal of op-amp (Pin-6).
6. Trace the wave form and note down the reading as per the
observation table.

Laboratory/School of Electronics
Engineering/KIIT/Manual Version-1.1
Basic Electronics Engineering
 measuring the
observation table for
OBSERVATION TABLE: The error is shown
calculation of
and
amplitude of the output voltage
below:
% of error
Type of Vi Vo Vo
amplifier (involt) (Practical)
(Theoretical)
(in volt)
in volt)
NON-
INVERTINNG ela
AMPLIFIER
INVERTING 's 2
AMPLIFIER

CONCLUSION:
To be written by the students.

VIVA QUESTION:

1. What do you mean by op-amp?

2. Define the properties of an ideal op-amp.
3. Define the properties of practical op-amp.
a

4. What is the virtual ground concept?

5. What is CMRR? Define its values for Ideal and
an practical op
amp.
6. Define the term inverting and non-inverting amplifier.
7. What are the different applications of op-amp?