An operational amplifier (op-amp) is a high-gain differential amplifier used for mathematical operations. It is available as an integrated circuit with dual inputs and a single output. An op-amp has several stages - an input stage that provides high voltage gain, intermediate stages that further increase gain, a level-shifting stage to center the output, and an output stage with high current capability. It is used in circuits due to its ideal characteristics like infinite gain, bandwidth and zero offset voltage.

2. What is an Operational Amplifier
It is a high gain direct coupled differential
amplifier i.e., it is a multistage amplifier in
which different stages are directly coupled.
 It is named as operational amplifier because
it was used for performing mathematical
operations.
It is available in the form of Integrated
Chip(IC) with different packages.
In short it is called Op-Amp.

3. Block diagram of Op-Amp
Input
Stage
Intermedi
ate Stage
Level
shifting
stage
Output
stage
Dual input
Balanced
output
Differential
amplifier
Dual input
Un-Balanced
output
Differential
amplifier
Emitter
follower with
constant
current
source
Complement
ary symmetry
push –pull
amplifier

4. Input stage- It consists of dual input balanced
output differential amplifier. This stage provides
the maximum amount of voltage gain of the Op-
Amp.
 Intermediate Stage – It consists of dual input
unbalanced output differential amplifier. This
stage increases the overall gain of the Op-Amp.

5. Level shifting stage – It consists of emitter
follower. It is used to shift the dc level at the
output of intermediate stage to zero.
 Output stage – It consists of complementary
symmetry push-pull amplifier which increases
the current supplying capability of the Op-
Amp.

6. Circuit Symbol
An Op-Amp generally has two inputs and
one output.
The two inputs are called inverting
input(denoted by – symbol) and non-
inverting input(denoted by + symbol).
Image source: http://www.ee.surrey.ac.uk/Projects/CAL/frequency-
response/idealopamp.html

7. Ideal Characteristics of Op-Amp
Infinite input resistance
Zero output resistance
Infinite bandwidth
Infinite slew rate
Infinite CMRR(Common Mode Rejection Ratio)
Infinite voltage gain
Zero output offset voltage
Characteristics should be independent of
temperature

8. Different packages of Op-Amp 741 IC
The Op-Amp IC’s are available in different
packages like 8-pin or 14-pin Dual in
Package(DIP),8-pin metal can, 10 pin flat pack.
The most widely used package of Op-Amp is 8-
pin Dual In Package.

9. Image Source:http://www.circuitstoday.com/introduction-to-ua-741-op-amp

10. Pin Configuration of Op-Amp 741
(8 pin DIP)
Image Source:http://www.circuitstoday.com/introduction-to-ua-741-op-amp

11. Pin Number Description
1 Offset Null
2 Inverting Input terminal
3 Non-inverting input terminal
4 Power supply negative
5 Offset Null
6 Output
7 Power supply positive
8 Not Connected

12. Pin 1 and Pin 5 – These pins are used to set output
offset voltage to zero i.e, to make output zero when
no inputs are given. A potentiometer is connected
between pins 1 and 5 and the resistance is adjusted
till the output voltage becomes zero.
Pin4 and Pin 7- These pins are used to give power
supply to the Op-Amp.
Pin 2 and Pin 3 – These pins are used to give input
voltages to the Op-Amp.
Pin 6- The output of the Op-Amp is taken at this
pin