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Op-Amp Modes
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EXPERIMENT NO: 7
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OP-AMP MODES : INVERTING &
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NON-INVERTING.
Mr. Prathamesh Bhosale.
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Op-Amp Modes
TITLE:- Op-Amp Modes: Inverting & Non-Inverting.
AIM:- To study & Analyze operation of Inverting & Non-Inverting Op-Amp
Modes.
APPERATUS:1. Experimental
Board,
Op-Amp
IC
741,
CRO/DSO,
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Multimeter, Specified components, etc.
Electronic
1. Trace the circuits of Op-Amp Modes;
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2. Observe Input & Output Voltage Waveform,
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OBJECTIVES:-
3. Change values of Feedback resistor during each sample reading, & then
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calculate as well as observed output voltage.
SECTION (1)
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CIRCUIT DIAGRAM:- (A) INVERTING AMPLIFIER
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NOTE : STUDENT SHOULD HAVE TO DRAW NEAT CIRCUIT DIAGRAM OF
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INVERTING AMPLIFIER.
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Op-Amp Modes
THEORY:- (A) INVERTING AMPLIFIER
An Inverting amplifier is the most widely used op-amp circuit in various
industrial applications. As shown in circuit diagram, The output voltage (Vo) is
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feedback to inverting input terminal through resistor “Rf” i.e. feedback resistor.
Where as input voltage is given via resistor ‘Rin’. Output voltage ‘Vo’ is obtained
Vo = Vin *(-Rf/Rin)
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by calculation, such as;
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Here, (-Rf/Rin) is nothing but gain of an op-amp. Negative sign indicates
that there is phase difference of 180 degree between Vin & Vo of an Op-Amp.
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to invert & amplify input voltage.
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Effective input impedance is Rin & Op-Amp used Negative Feedback Resistor Rf
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Feedback arrangement is responsible for allowing the some of the output
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signal return to the input, since output is 180 degree out of phase with input supply
voltage. Input voltage ”Vin” is provided with help of 1kHz sine wave from
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function generator. Generated input voltage & output Voltage is observed on CRO.
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& for various values of change in Feedback resistor, we tabulate the readings &
compare with theoretical Values.
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Basically we have to calculate followings for analysis of Inverting
Amplifier;
(i)
Gain = (-Rf / Rin)
(ii)
Vo = Vin* (-Rf / Rin)
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Op-Amp Modes
SECTION (2)
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CIRCUIT DIAGRAM:- (B) NON-INVERTING AMPLIFIER
NOTE : STUDENT SHOULD HAVE TO DRAW NEAT CIRCUIT DIAGRAM OF
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NON-INVERTING AMPLIFIER.
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THEORY:- (B) NON-INVERTING AMPLIFIER
The Second basic configuration mode of an Op-Amp circuit is that of Non-
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Inverting operational amplifier. In this mode of operation the input voltage ‘Vin’ is
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applied directly to the non-inverting terminal of Op-Amp, it is responsible for
output gain of Op-Amp become positive in value, & it is contrast to the ‘Inverting
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amplifier’ circuit which saw previously.
The result of thin non-inverting mode of Op-Amp is that the output signal is
“In-Phase” with the input signal. Feedback control of non-inverting Op-Amp is
achieved by applying a small part of the output voltage signal back to the inverting
terminal via Rf & R1 voltage divider network.
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Op-Amp Modes
Here also, Generated input voltage & output Voltage is observed on CRO. &
for various values of change in Feedback resistor, Then, we have to tabulate the
readings & compare with theoretical Values.
Basically here, we have to calculate followings, for analysis of Non-
(ii)
Vo = Vin* {1+(-Rf / R1)}
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Gain (Av) = 1+(-Rf / R1)
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(i)
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Inverting Amplifier;
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PROCEDURE:-
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1. Trace the circuit & draw accordingly in notebook. Also, find the values of
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resistor, IC & note down it accordingly.
2. Supply this Op-amp IC 741 with, dual power supply voltage in terms of
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+ Vcc & -Vee. (Say 12 V).
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3. Give the supply input voltage “Vin” of 1kHz sine wave from function
generator.
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4. Observe the output voltage “Vo” on CRO as well as at the same time
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observe the input supply voltage “Vin” also on same CRO by using dual
channel arrangement.
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5. Vary feedback resistor values and measure corresponding output voltage
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“Vo”
6. Tabulate reading based on components used & formulation specified for
circuit designed as well compare theoretical calculations with observed
waveforms.
7. Prepare Graph for each mode of operation for observed waveforms.
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Op-Amp Modes
OBSERVATIONS & CALCULATIONS:1. For Inverting Amplifier mode calculate; (For Each Value of “Rf”)
(i)
Gain (Av) = 1+(-Rf / R1)
(ii)
Vo = Vin* {1+(-Rf / R1)}
Observation Table for Inverting Amplifier Mode:
Gain =
No.
“Rf”
1+(-Rf / R1)
Output Voltage
(Vo)
(Vo)
Vo = Vin* {1+(-Rf / R1)}
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Value of
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Calculated Output Voltage
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Observed
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2. For Non-Inverting Amplifier mode calculate; (For Each Value of “Rf”)
Gain = 1+(Rf / R1)
(ii)
Vo = Vin* {1+(-Rf / R1)}
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(i)
Observed Output
Voltage (Vo)
1+(Rf / R1)
Voltage (Vo)
Vo = Vin* {1+(-Rf / R1)}
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No.
Value of “Rf”
Calculated Output
Gain =
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Observation Table for Non-Inverting Amplifier Mode:
1
2
3
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Op-Amp Modes
3. Observed wave form on CRO/DSO ;
NOTE : Student should have to DRAW observed waveform on GRAPH
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PAPER neatly ,which they were OBSERVED on CRO/DSO.
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RESULTS:-
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1. The output waveform of inverting amplifier mode of op-amp is 180 degree
out of phase with input supply voltage waveform.
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2. The output waveform of Non-Inverting amplifier mode of op-amp is in
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phase with input supply voltage waveform.
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SAMPLE VIVA QUESTIONS:-
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1) Why IC741 called Operational Amplifier?
2) Explain various operating modes of op-amp.
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