1. or Op Amps for short
By Mohammed Imran,
Assistant Professor, EED, MJCET

2. What is an Op-Amp? – The
Surface
An Operational Amplifier (Op-Amp) is an
integrated circuit that uses external
voltage to amplify the input through a very
high gain.
We recognize an Op-Amp as a mass-
produced component found in countless
electronics.
What an Op-Amp looks
like to a lay-person
What an Op-Amp looks
like to an engineer

3. What is an Op-Amp? – The Layout
There are 8 pins in a common Op-Amp, like
the 741 which is used in many instructional
courses.

4. Symbols for Ideal and Real Op Amps
OpAmp uA741
LM111 LM324

5. Terminals on an Op Amp
Non-inverting
Input terminal
Inverting input
terminal
Output terminal
Positive power supply
(Positive rail)
Negative power supply
(Negative rail)

6. What is an Op-Amp? – The
InsideThe actual count varies, but an Op-Amp
contains several Transistors, Resistors, and
a few Capacitors and Diodes.
For simplicity, an Op-Amp is often
depicted as this:
Non-
Inverting
Input
Inverting
Input
Positive
Power
Supply
Negative
Power
Supply
Output
-
+

7. vd = v2 – v1
A is the open-loop voltage
gain
v2
v1
Voltage controlled
voltage source

8. Typical Op Amp Parameters
Parameter Variable Typical
Ranges
Ideal Values
Open-Loop
Voltage Gain
A 105
to 108
∞
Input
Resistance
Ri 105
to 1013
Ω
∞ Ω
Output
Resistance
Ro 10 to 100 Ω 0 Ω
Supply
Voltage
Vcc/V+
-Vcc/V-
5 to 30 V
-30V to 0V
N/A
N/A

9. How to Find These Values
Component Datasheets
Many manufacturers have made these freely available
on the internet
 Example: LM 324 Operational Amplifier

12. Large Signal Voltage Gain = A
Typical
A = 100 V/mV = 100V/0.001V = 100,000
Minimum
A = 25 V/mV = 25 V/0.001V = 25,000

13. Voltage Transfer Characteristic
Range where
we operate
the op amp as
an amplifier.
vd

14. Ideal Op Amp
i2 = 0
i1 = 0
Because Ri is equal to
∞Ω, the voltage across Ri
is 0V.
v1 = v2
vd = 0 V
v1
v2

15. Almost Ideal Op Amp
Ri = ∞ Ω
Therefore, i1 = i2 = 0A
Ro = 0 Ω
Usually, vd = 0V so v1 = v2
The op amp forces the voltage at the inverting input
terminal to be equal to the voltage at the noninverting input
terminal if there is some component connecting the output
terminal to the inverting input terminal.
Rarely is the op amp limited to V-
< vo < V+
.
The output voltage is allowed to be as positive or as negative
as needed to force vd = 0V.

16. Op Amps Applications
Audio amplifiers
Speakers and microphone circuits in cell phones,
computers, mpg players, boom boxes, etc.
Instrumentation amplifiers
Biomedical systems including heart monitors and
oxygen sensors.
Power amplifiers
Analog computers
Combination of integrators, differentiators, summing
amplifiers, and multipliers