The operational amplifier, or op-amp, is a basic building block of analog electronic circuits that amplifies the difference between its input terminals. It has very high gain, typically around 100,000, and its output depends on the difference between the voltages at its two input terminals. By using negative feedback, most of the open-loop gain is canceled out, making the op-amp useful for various applications like non-inverting and inverting amplifiers, adders, integrators, and differentiators. An ideal op-amp has infinite gain, bandwidth, and input impedance and zero output impedance. Practical op-amps have limitations compared to the ideal but can still perform signal amplification and processing functions.

1. OPAMP...
OPerational AMPlifier

2. Intro...
● Op-amps are among the most widely used electronic devices
today.
● One of the basic building blocks of Analogue Electronic
Circuits.
● A DC-coupled high-gain electronic voltage amplifier.
● Has a differential input and, usually, a single-ended output.
● High open loop gain, typically it is ~ 10^4-10^5.
● By using negative feedback, we throw most of that away!

6. ● An ideal Operational Amplifier is basically a three-terminal
device which consists of two high impedance inputs.
● One called the Inverting Input, marked with a negative or
"minus" sign, ( - ) and the other one called the Non-inverting
Input, marked with a positive or "plus" sign ( + ).
● The output signal is the amplification factor, known as the
amplifiers gain ( A ) multiplied by the value of the input signal.
Vo=A(V+ - V-)

7. ➔ A generalized form of a differential amplifier:
● V1,V2: Inputs
● The two identical transistors TR1
and TR2 are both biased at the same
operating point with their emitters
connected together and returned to
the common rail, -Vee by way of
resistor Re.
● The circuit operates from a dual
supply+Vcc and -Vee which
ensures a constant supply.
● Vout=V1-V2
Equivalent Circuit for Ideal Operational Amplifiers:
-
● V1 : Inverting input
● V2: Inverting input
● A: Gain
● Vdiff: V1-V2
● +Vsupply: +ve power supply
● -Vsupply: -ve power supply

13. Properties of ideal op amp...
● Infinite open-loop gain
● Infinite voltage range available at the output
● Infinite bandwidth with zero phase shift and infinite slew
rate
● Infinite input impedance. So zero input current and zero
input offset voltage
● Zero output impedance
● Zero noise
● Infinite Common-mode rejection ratio (CMRR)

14. Common-Mode Operation
● Same voltage source is applied at
both terminals
● Ideally, two input are equally amplified
● Output voltage is ideally zero due to differential voltage is
zero
● Practically, a small output signal can still be measured
● Note for differential circuits:
○ Opposite inputs : highly amplified
○ Common inputs : slightly amplified
Common-Mode Rejection

16. Single-Ended Input
● + terminal : Ground
● – terminal : Source
● 180o
phase change
● + terminal : Source
● – terminal : Ground
● 0o
phase change

17. Ideal Practical
Open Loop gain A µ
10
5
Bandwidth BW µ 0-100Hz
Input Impedance
Z
in
µ >1MW
Output Impedance
Z
out
0 W 10-100 W
Output Voltage
Vout
Depends only on V
d
=
(V
+
-V
-
)
Differential mode signal
Depends slightly on
average input V
c
=
(V
+
+V
-
)/2 Common-
Mode signal
CMRR µ 10-100dB
IDEAL
v/s
PRAC
TICAL

20. IC Product
DIP-741
Dual op-amp 1458
device

21. 741

22. Applications
•Non Inverting Amplifier
•Inverting Amplifier
•Adder (Summing amp)
–(and Subtractor using an Inverter)
•Differential Amplifier
•Integrator
•Differentiator

23. Noninverting amplifier Inverting amplifier
Voltage follower
Less than unity gain
Vo=Vi
Vo = 1+(Rf/Ra)Vi Vo = 1+(Rf/Ra)(R1/(R1+R2)Vi

31. Differential amplifier