In this ppt, we tried our best to give the basic knowledge of Operational Amplifier and its two types.

1. Electronics and
Electronic Instrument:
Operational Amplifier,
Differential Amplifier,
Summing Amplifier
M Shakir
17441510-059
Ahmad Islam
17441510-074
Ali Raza
17441510-080
Osama Munwar
17441510-098

2. OPERATIONAL
AMPLIFIER
University Of Gujrat 2

3. History
◦ The operational amplifier concept originated around 1947. It was proposed that such a device would form
an extremely useful analog building block.
◦ The first commercial op-amps used vacuum tubes, but it was not until the introduction of the integrated
circuit did the op-amp start to fulfill its true potential.
◦ In 1964, the first integrated circuit op-amp, designated the 702, was developed by Fairchild
Semiconductor.
◦ But after 702 manufacture using this knowledge a more of 709 and 714 is manufactured, which has
become an industry standard.
University Of Gujrat 3

4. OP-AMP
◦ The Operational Amplifier (OP-AMP) symbol is shown in Figure. It has two input terminals, the
inverting (-) input and the non-inverting (+) input, and one output terminal. Most OP-AMP operate with
two dc supply voltages, one positive and the other negative.
University Of Gujrat 4

5. OP-AMP input Modes and Parameters
MODES
◦ Differential Mode
In the Differential mode, either one signal is
applied to an input with the other input grounded or
two opposite-polarity signals are applied to the inputs.
When an op-amp is operated in the single-ended
differential mode, one input is grounded and a signal
voltage is applied to the other input.
◦ Common Mode
In the Common mode, two signal voltages
of the same phase, frequency, and amplitude are
applied to the two inputs.
PARAMETERS
◦ Common Mode Rejector Ratio (CMRR)
Unwanted signals (noise) appearing with the same
polarity on both input lines are essentially cancelled by the op-
amp and do not appear on the output. The measure of an
amplifier’s ability to reject common-mode signals is a parameter
called the CMRR (common-mode rejection ratio).
◦ Input Bias Current
The input bias current is the average of both input
currents.
◦ Input Offset Voltage
The Input offset voltage, 𝑉𝑜𝑠, is the differential dc
voltage required between the inputs to force the output to zero
volts.
University Of Gujrat 5

6. University Of Gujrat 6
𝐶𝑀𝑅𝑅 =
𝐴𝑜𝑙
𝐴𝑐𝑚
𝐶𝑀𝑅𝑅 = 20 log
𝐴0 𝑙
𝐴𝑐𝑚
CMRR Equation
CMRR Equation in (db)
Single ended Differential Mode
Double ended Differential Mode
Common Mode
𝐼 𝐵𝐼𝐴𝑠 =
𝐼1 + 𝐼2
2
Figure and Eq. of Input Bias Current

7. Types
OP- AMP
Summing
Differential
University Of Gujrat 7

8. SUMMING AMPLIFIER
University Of Gujrat 8

9. Definition
◦ The Summing Amplifier is another type of operational amplifier circuit configuration that is used to combine
the voltages present on two or more inputs into a single output voltage.
◦ We in the inverting operational amplifier that the inverting amplifier has a single input voltage (Vin) applied
to the inverting input terminal.
◦ If we add more input resistors to the input, each equal in value to the original input resistor (Rin) we end up
with another operational amplifier circuit called a Summing Amplifier.
University Of Gujrat 9

10. Circuit Diagram
University Of Gujrat 10

11. Equations
University Of Gujrat 11

12. Examples
◦ Find the output voltage of the following Summing Amplifier circuit use the formula for the gain of the circuit.
University Of Gujrat 12

13. Cont…..
◦ We know that the output voltage is the sum of the two amplified input signals and is calculated as
◦ Then the output voltage of the Summing Amplifier circuit above is given as -45 mV and is negative as it an
inverting amplifier.
University Of Gujrat 13

14. Advantages and Disadvantages
Advantages
◦ Noise cancelation property.
◦ Reduce External Interferance
Disadvantages
◦ Complex Circuit
◦ Proper Biasing
University Of Gujrat 14

15. DIFFERENTIAL
AMPLIFIER
University Of Gujrat 15

16. Introduction
◦ A differential amplifier amplifies the difference between the two input signals. It is widely used in
the integrated circuits as an amplifier.
◦ It is an analog circuit with two inputs and one output in which the output is ideally proportional
to the difference between the two voltages
◦ The first stage of the op-amp is also a differential amplifier
◦ The input signal to a differential are defines as
1) Differential mode signal
2) Common mode signal

17. .

18. .

19. Advantages of Differential Amplifier:
◦ The ideal differential amplifier eliminates the common-mode signal at the output and only
amplifies the differential input. Using the differential amplifier it is possible to eliminate or reduce
any noise or interference which is common to both input terminals.
◦ When multiple differential amplifier stages are cascaded together, then it also eliminates the use
of coupling capacitors between each stage

20. Applications
◦ It is used as a series negative feedback circuit by using op amplifier
◦ Generally, we use differential amplifier that acts as a volume control circuit.
◦ The differential operational amplifier can be used as an automatic gain control circuit.
◦ Some of the differential operational amplifier can be used for Amplitude modulation.
◦ These amplifiers are used in an audio mixer to add different signals with equal gains.
◦ There are various resistors are used at the input of the summing amplifier to give a weighted sum.
◦ Summing amplifier is used to combine the signals. These amplifiers add the signals directly or scale them to fit some
prearranged combination rule.
◦ This amplifier is used to apply a DC offset voltage with an AC signal voltage. This process can be done in an LED
modulation circuit to maintain the LED in its linear operating range.
University Of Gujrat 20