To construct the operational amplifier by using discrete components and study as frequency response.

1. LAB MANUAL
Experiment Name:
T
oconstruct the operational amplifier by using
discrete components and study as frequency
response.

2. Amplifier and Discrete
components
O Amplifier: is an electronic device that increases the voltage,
current, or power of a signal. Amplifiers are used in wireless
communications and broadcasting, and in audio equipment
of all kinds.
O Discrete components: An elementary electronic device
constructed as a single unit. Before the advent of
integrated circuits (chips), all transistors, resistors,
capacitors and diodes were discrete. Discrete components
are widely used in amplifiers and other electronicproducts
that use large amounts ofcurrent.

3. Operational Amplifier
O Introduction: operational amplifier, also called
as an op-amp or op amp .
O It is designed for performing operationslike
addition, subtraction, integration,
differentiation etc.
O Amplifier is a voltage amplifying device
designed to be used with components like
capacitors and resistors, between itsin/out
terminals

4. Operational
Amplifier(741)
O 741 Op Amp IC is amonolithic integrated circuit.
O It was first manufactured byFairchild
semiconductors(company) in 1963.
O 741 indicates that this op-amp IC has 7 functional
pins, 4 pins capable of taking input and 1 output
pin.
O 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
integrators & summing amplifiers>

5. Operational Amplifier by
using discrete components
O Pin diagram
O standard 741 operational amplifier iscomposed
of 20 transistors and 11 resistors.
O All of them are integrated into a monolithicchip.

6. Circuit diagram of
Operational Amplifier(741)

7. OT
ounderstand the internal circuitrylet’s
divide circuit into different blocks.
1. Blue block comprises of adifferential
amplifier.
2. Red block comprises currentmirrors.
3. Magenta comprise of class Aamplifier
(voltage amplifier)
4. Green and cyan blocks comprises of alevel
translator and output amplifier.

8. Continued
O let’s understand each of theblocks:
Deferential amplifier: NPN emitter follower Q1& Q2 which
provides high input impedance and provide gain. Common
base Q3 & Q4 PNP transistors which are used to drive the
active load Q7, Q5, and Q6. Q5 and Q6 perform function of
the differential amplifier for the offset null input signal. The
current of Q5 & Q6 is controlled by varying a 10k pot
connected between input pins 1&5. Q1&Q3 are in series and
Q2&Q4 is in series which provides high gain when the input is
applied at its input terminals. It can reject common signals

9. O Current mirrors(red block): Current mirrors
comprise of (Q8-Q9) and (Q12-Q13) areconfigured
as Wilson current mirror. Whereas,transistors
Q10-Q11 are configured aswider current mirror
these current mirrors maintain constant currentto
the circuit for stable operation.
O voltage amplifier(Magenta block): Q15&Q19
provides voltage gain, transistor Q22 is used to
prevent excess current provided toQ20.
• Q16 along with 4.5k and 7.5k resistor (known as
voltage level shifter), this circuit uses to prevent
the output signal fromdistortion.

10. Continued
O Output amplifier: contain Q14, Q17&Q20 transistor. Q14 &
Q20 provides output impedance (typically50-75
Ohms) and current gain. Q17 limits the current at the
output.
current from Q8 and Q9 is divided into the differential
amplifier comprises of (Q1-Q3) & (Q2-Q4). Now the current
from the Q3&Q4 is summed with the current of Q10&Q11, Q7
is used to drive Q5 and Q6. The quiescent current is set in
Q16 and Q19 is set due to Wilson current mirror (Q12&Q13).
The value of 30pFis used for frequency compensation.

11. CONFIGURATION OF OP-AMP(IC
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womain configurations o
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O 1) Open-loopconfiguration
2) Close-loopconfiguration
1) Open-loop configuration: in this configuration 741IC can
be used as a very high gain amplifier. In open-loop, the
gain is ideally infinite hence the output will saturateeither
in positive supply voltage or in negative supply voltages.
This open-loop system hasthree basic configurations:
a)DIFFERENTIAL AMPLIFIER: In this input is applied at both
the inputs, which will amplify the difference b/w the two
inputs.

12. Continued
b)NON-INVERTING AMPLIFIER: The input is appliedat
the non-invert input terminal. The gain can be
calculated using the value of resistors. Rf is feedback
resistor.
Av= 1+ (Rf /R1)
c)INVERTING AMPLIFIER: the input is appliedat
inverting terminal. Av= – (Rf / R1)
2)Close-loop configuration: in this configuration, it is
connected as negative feedback arrangement. The
feedback network is through aresistor.

13. CHARACTERISTICSOF IC741(OP-AMP):
The characteristics of the IC 741 operational amplifierinclude
the following
O The Input impedance of the IC 741 op amp is above
100kilo-ohms.
O The o/p of the 741 IC op amp is below 100 ohms.
O The frequency range of amplifier signals for IC 741op amp
is from 0Hz- 1MHz.
O The offset current and offset voltage of the IC 741 op amp
is low
O The voltage gain of the IC 741 is about 2,00,000.

14. FREQUENCYRESPONSE:
O Frequency response is the quantitative measure of the
output spectrum of a system or device in response to a
stimulus, and is used to characterize the dynamics of the
system.
O In open loop, In open loop, the op-amp 741 has very high
gain, this response is not very good. T
oimprove the gainwe
apply negative feedback network, by applying a negative
feedback network the gain starts to fall away quite
dramatically. The gain is not constant and varies
depending on the frequency of input signal. The below
graph illustrates the relation betweenthem

15. gain remains constant at around 200,000 when the operational
amplifier is operated at frequencies below 10Hz. As the frequencyof
input signal increases, the gain reduces and approaches unity at
frequencies around 100,000Hz.
The gain is not constant and varies depending on the frequency
of input signal. The below graph illustrates the relation between
them