1. Definition of OP-AMP OP-Amp:
OP-AMP(Operational Amplifier) is an amplifier which is used to perform a variety of operations such as amplification, addition, subtraction, differentiation, integration etc.
It was first used by John R. Ragazzini in 1947.
It consists 20 Transistors, 11 resistor, & 1 capacitor.

2. OP-AMP consists 20 Transistor, 11 resistor &
1 capacitor.

3. Block Diagram of OP-AMP

4. CHARACTERSTIC OF OP-AMP
Very high input resistance or even infinity which produces negligible current at the input.
Very high current gain.
Very low output impedance or even zero, so as not to affect the output of the amplifier by loading.
Nowadays, OP-AMP is used in Analog Computers and in Timing circuits.

5. Physical Appearance of OP-AMP
It has 8 pins.

6. Circuit symbol of OP-AMP
It has 7 pins & explanation of pins are as follow in next slide.

7. Pins & there explanation
Pin no.1 & 5:
It is +ve & -ve offset voltage used to nullify output voltage.
Pin no. 2 & 3:
It is inverting & non-inverting input terminals of OP-AMP.
Pin no. 4 & 7:
It is used to give dc supply to OP-AMP.
Pin no. 6 & 8:
It is always output of OP-AMP & Pin no. 8 is Not connected to balance an OP-AMP.

8. Why OP-AMP isn’t used in Open Loop
Gain in the Open loop is very large (2,00,000).
Hence, the value “Vd “ is driven in saturation region.
Thus, output voltage is distorted because output voltage can’t be higher then ±Vsat.
Hence, OP-AMP is not used in Open loop configuration.

9. Difference between Open loop & Closed loop
No Feedback.
High Voltage gain.
Output waveform is distorted.
It is used in Comparator.
Positive or negative feedback.
Low Voltage gain.
Output waveform is not distorted.
It is used in linear amplifier, oscillator etc.

10. Ideal Characteristics of OP-AMP
Input resistance (Ri)= ∞ Ω
Output resistance (Ro) = 0 Ω
Voltage gain (Av) = ∞
Bandwidth (B) = ∞
CMRR = ∞
Slew Rate (S) = ∞
Offset Voltage= 0
PSRR = 0

11. OP-AMP as an Inverting Amplifier
The input signal is applied to the inverting input terminal.
A resistor R1, is connected to the inverting input.
The feedback resistor R2 is connected between the output and the inverting input.

12. Input & Output waveform of OP-AMP

13. Expression for Inverting Amplifier
Accord. to Virtual Ground concept we can write:
Input voltage is given by, Vi= IRi.
Output voltage is given by, Vo= -IRf.
Closed loop gain, Avf = (Vo/Vi).
Hence, Avf = -(Rf/Ri).
Vo = -(Rf/Ri) x Vi
Above equation shows that output voltage is 180˚out of phase with the input voltage.

14. Non-Inverting Amplifier
The input signal is applied to the non inverting input terminal.
A resistor R1, is connected from the inverting input to the ground.
The feedback resistor R2 is connected between the output and the inverting input.

15. Input & Output Waveforms of NINV OP-AMP

16. Expression for NINV OP-AMP
Voltage across R1, Vi = [R1/(Rf + R1)] x Vo.
Closed loop gain, Av = Vo/Vi.
Hence , Av = 1 + (Rf/R1).
Thus, Vo = Av x Vi.
Above equation shows that output & input voltage will be in phase.

17. OP AMP as Integrator

18. OP AMP as Integrator
In OP AMP as an Integrator, capacitor is connected at feedback i.e. Output is taken at the Capacitor.
At input terminal only one resistor is connected.
Since output is Integration of Input, name is Integrator.

19. Advantages of OP-AMP
It can perform different types of mathematical operations.
Small in size.
High reliability.
Less power consumption.
Easy to replace.
Reduced cost.

20. Applications of OP-AMP
Multipliers.
Multivibrators.
Timers.
Log and Antilog amplifier.
Waveform generators.
Integrator.
Differentiator.