1. Topic: Operational Amplifiers
Mahatma Phule Arts, Science And Commerce College, Panvel
( Academic Year 2015 – 2016 )
SEMESTER SECOND
F. Y. B. Sc.
Topic: Operational Amplifiers
Fig 12-1 a&b op-amp schem. symbols By
Dr. Sarode M. T.
Department of Physics
09/01/2015
13/01/2015
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2. Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
Introduction
The operational amplifier or op-amp is a circuit of components integrated into one chip.
A typical op-amp is powered by two dc voltages and has an inverting(-) and a non-inverting input (+) and an output.
An op amp is an electronic device which provides a voltage output based on the voltage input
Fig 12-1 a&b op-amp schem. symbols
09/01/2015
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
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3. Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
Basic op-amp
Op-amp has two inputs that connect to two terminals
and one output
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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4. Operational Amplifiers
Five important pins
2 – The inverting input
3 – The non-inverting input
6 – The output
4 – The negative power supply V- (-Vcc)
7 – The positive power supply V+ (+Vcc)
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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5. Operational Amplifiers
The output of the op amp is given by the following equation:
Vd = E1 – E2
and Vo = AVOL(Vd)
AVOL is called the open-loop voltage gain because it
is the gain of the op amp without any external feedback from output to input
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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6. Operational Amplifiers
Positive Saturation – where the output voltage exceeds the positive power input
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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7. Operational Amplifiers
Linear Region – where the output voltage is linear based on A (gain)
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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8. Operational Amplifiers
Negative Saturation – where the output voltage would be less than the negative power input
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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9. Operational Amplifiers
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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10. What do they really look like?
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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11. Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
IC Circuit
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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12. Operational Amplifiers
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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13. Operational Amplifiers
An ideal op-amp has infinite gain and bandwidth, we know this is impossible.
However, op-amps do have:
very high gain
very high input impedance(Zin = ∞)
very low output impedance (Zout = 0)
wide bandwidth.
Fig 12-2a&b ideal and practical op-amp
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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14. Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
Application in op-amp
There are 2 types of application in op-amp
Linear application
Non-linear application
Linear application is where the op-amp operate in linear region:
Assumptions in linear application:
Input current, Ii = 0
Input voltage: V+=V-
Feedback at the inverting input
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015

15. Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
Application in op-amp
Non-linear application is where the op-amp operate in non-linear region
By comparing these two input voltages: positive input voltages, V+ and negative input voltage, V- where:
VO = VCC if V+ > V-
VO = -VEE if V+ < V-
Input current, Ii = 0
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015

16. Applications of op-amp
Comparator (Pembanding)
Inverter (Penukar)
Audio amplifier (Penguat Audio)
Difference Amplifier (Penguat Beza)
Filter (Penapis)
Summing Amplifier (Penguat Jumlahan)
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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17. Op-amp Circuit Application
Penguat menyongsang
Penguat tidak menyongsang
Penambah menyongsang
Pengikut voltan
Penguat penolak
Penguat instrumentasi
Pengamil
Pengkerbezaan
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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18. Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
Op-amp Circuit Application
Inverting Amplifier
Non-Inverting Amplifier
Summing Amplifier
Unity Follower
Difference Amplifier
Integrators
Differentiators
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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19. Application: Inverting amplifier
Provide a constant gain multiplier
Input signal is connected to the inverting input of the op-amp. Therefore, the output signal is 180 degree out of phase from the input signal
Rf is the feed-back resistor to control the voltage gain of the op-amp
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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20. Summary of op-amp behavior
Vo = A(V+ - V)
Vo/A = V+ - V
Let A infinity
then,
V+ - V
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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21. Summary of op-amp behavior
V+ = V
I+ = I  = 0
Seems strange, but the input terminals to an
op-amp act as a short and open at the same time
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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22. To analyze an op-amp circuit for linear operation
Write node equations at + and - terminals
(Ii=I+ = I- = 0)
Set V+ = V-
Solve for Vo
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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23. Analysis of inverting amplifierIi I1
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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24. Application:Non-inverting amplifier
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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25. Non-inverting configurationVi I1 I2 Ii
09/01/2015
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C College, Panvel
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26. Application: Summing amplifier
Virtual-ground equivalent circuit.
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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27. Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
Summing Amplifier V1 V2 V3 R1 R2 R3 Rf
This circuit is called
a weighted summer
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015
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28. Application: Unity Follower(Pengikut Voltan)
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015

29. Application: Difference amplifier (Penguat Penolak)
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015

30. Application: Instrumentation Amplifier (Penguat Instrumentasi)
Buffer (Penimbal)
Difference amplifier
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015

31. Application:Integrator (Pengamil)
Feedback component = capacitor : Integrator
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015

32. Application: Differentiation (Pengkerbezaan)
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015

33. Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
Exercise 1
Find VO?
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015

34. Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
Exercise 2
Find V2 and V3?
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015

35. Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
Exercise 3
Find VO?
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015

36. Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
Exercise 4
Find VO?
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015

37. Recall: Non-linear application in op-amp
Non-linear application is where the op-amp operate in non-linear region
By comparing these two input voltages: positive input voltages, V+ and negative input voltage, V- where:
VO = VCC if V+ > V-
VO = -VCC if V+ < V-
Input current, Ii = 0
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015

38. Non-linear application: Comparator (Pembanding)
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015

39. Non-linear application: Comparator (Pembanding)
(a) Input Voltage of Comparator
Vo(V) 10 -5 t
VS(V)
Compare V+ and V-
V+=0
V-=VS
When:
VS>0,V+>V- so Vo=10V
VS<0,V+<V- so Vo=-5V
(b) Output Voltage of Comparator
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015

40. Non-linear application Schmitt Trigger (Pemicu Schmitt)
Positive Feedback - +
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015

41. Non-linear application Schmitt Trigger (Pemicu Schmitt)
(b) Input Voltage of Schmitt Trigger
Vo(V) 15
-15 t
VS(V)
7.5
-7.5
(a) Transfer Characteristic of Schmitt Trigger
Vo(V)
VS(V)
-7.5
7.5
-10 10 15
-15
(c) Output Voltage of Schmitt Trigger
Dr. M. T. Sarode Dept. Of Physics, M.P.A.S.C>College, Panvel
09/01/2015