OpAmp PPT presentation in college

1. OPERATIONAL AMPLIFIER
PRESENTING BY—
MANMOHAN SINGH
M.SC.(PHYSICS)

2. CONTENT–
• Introduction
• What is an Operational amplifier
• Characteristic Properties of Op Amp
• Circuit symbol of op amp
• Working of op amp
• Applications of op amp
• Advantage and disadvantages

3. DEFINITION
An Operational amplifier is a high gain
amplifier
Used to perform a variety of function.
It consists of two Input and One output

4. BASIC INFORMATION OF OP AMP
Op amp have some basic information–
• Two input terminals
1.Inverting terminal
2.Non inverting terminal
• one output terminal
• Two power supply terminals (+VE and – VE supply)

5. CIRCUIT SYMBOL —
Vout = A(V1 –V2)
A= – Vo/ Vi
A = Zf / Z1
A =Rf / R1
A is voltage gain

6. IMAGE OF OP AMP

7. PROPERTIES–
IDEAL OP AMP
1. Infinite Input Impedance
2. Infinite Voltage gain
3. Infinite band width
4. Zero output impedance
5. Perfectly balanced circuit i.e. when both the input signals are identical the
output voltage is zero
6. Perfectly stable i.e. due to changes in temperature, voltage etc.The
characteristics properties do not change

8. PRACTICAL OP AMP
1. Input impedance 500k-2M ohm
2. Output impedance 20-100 ohm
3. Open-loop gain (20k to 200k)
4. Bandwidth limited (a few kHz)
5. Has noise contribution
6. Non-zero DC output offset

9. WORKING
The Amplifier’s input consists of a V+ input and a V- input ,and Ideally the op -
amp amplifies only the difference in voltage Between the two, which is called
the differential input the output voltage of the op amp is given by the equation:
Vout =AOL (V+ – V– )
Where is V+ is the Voltage at the non-Inverting terminal,V- is voltage at the
inverting terminal and AOL is the open loop gain of the amplifier( the term “open
loop” refers to the absence of a feedback loop from the output to the input).
The magnitude of AOL is typically very large—100,000 or more for integrated
circuit OPAMP and therefore even a quite small difference between V+ and V-
drives the amplifier output nearly to the supply Voltage.

10. INVERTING AMPLIFIER
Applying the rules: terminal at “virtual ground” so current through R1 is
If=Vin/ R1
• Current does not flow into op amp
– so the current through R1 must go through R2
– Voltage drop across R2is then IfR2 = Vin (R2/R1)
So Vout=0
• Thus we amplifies Vin by factor R2/R1
(–) sign earns title ”inverting amplifier
• Current is drown into Op Amp output terminal

11. NON INVERTING AMPLIFIER
• Negative terminal held at Vin
– show current R1 is If=Vin/R1 (to left,Into ground )
• This current cannot come from op amp input
– so comes throw R2 (delivered from op amp output)
– voltage drop across R2 is If = Vin (R2/R1)
– so that output is higher than negative
input terminal by
– Vout = Vin +Vin (R2/R1)
– Thus, gain is ( 1+ R2 /R1 ), And is positive
• Current is source from op amp output in this example

12. APPLICATION
• Unity gain amplifier (Buffer)
• The differentiator amplifier
• The integrator amplifier
• The summing amplifier (adder)
• Comparator
• Substractor
• Voltage regulator
• Analog calculator
• Waveform generators
• Use in electronics system design

13. 1.UNITY GAIN AMPLIFIER (BUFFER)
• Gain is 1 because no feedback or input resistors are used .
• Gain =Vout/Vin = RF/Rin =1
• Application: it is used where circuit isolation is required ( very high
input impedance)

14. 2.THE DIFFERENTIATOR AMPLIFIER
• The basic Operational amplifier differentiator circuit produces an
output signal which is the first derivative of the input signal.
• I1=C d(vi)/dt
• I2= –Vo(t)/ R
• I1=I2
• So, Vo (t) = –RCdVi(t)/ dt

15. 3.INTEGRATOR AMPLIFIER
The integrator Op Amp produces an output
voltage that is both proportional to the amplitude
and duration of the input signal.
I1=Vi(t)/R
I2=–C d[Vo(t)]/dt
I1=I2
Vo(t) =–1/RC Vi(t) dt

16. 4.THE SUMMING AMPLIFIER (ADDER)
• When more then one voltage is applied
At terminal 1 the negative feedback of
Inverting op amp.
In this case the output voltage is equal to
the sum of the input voltage.
IA= VA / R A, IB = VB /RB , Ic = Vc /Rc
I1=IA +IB +Ic
I2= –Vo/RF
I1=I2
Vo = –Rf/R (VA +VB +Vc )

17. 5. COMPARATOR
• Op amp can be used
to Comparator a signal
Voltage with reference voltage.
• The circuit for this purpose called Comparator.
Vo = Vos + VoR
Vo = –A( Vs – VR )

18. 6.OPAMP AS A CURRENT SOURCE
• A current source can be made from
• An Inverting amplifier As shows in figure.
• The current In the load Resistor, Ro must be equal to current In
R1.
• The current is then obtain by dividing the input voltage By R1 .

19. 7. SUBSTRACTOR
• In this circuit of op amp shown in figure when to
voltages are fed at the input the
In proportional to the difference of the
two inputs .thus the circuit can be used as a
Substractor.
Vo= V01 + V 02 = Rf/ R1 (V2–V1)

20. ADVANTAGES
• The use of negative feedback makes it easy to
adjust the voltage gain.
• The voltage gain obtained is practicable.

21. DIS-ADVANTAGES
• The disadvantages are the loss of voltage gain and the
need for a high impedance differential amplifier circuit.
• with the Op Amp these disadvantages are no longer
valid,and most amplifier systems are designed using
OpAmp with a negative feedback loop to control the gain.

22. COMMON MODE REJECTION RATIO
CMRR= gain for difference signal = Ad/Ac
gain for common mode signal
The average value of the two currents following into the
op amp terminals .
It’s value is 90db