Op. Amps Applications
The Inverting Configuration
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The Noninverting Configuration
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The Voltage follower
(a) The unity-gain buffer or follower amplifier.
(b) Its equivalent circuit model.
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The Weighted Summer
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The Weighted Summer
Ra Rc
Ra Rc
Rc
Rc
vo  v1 ( )( )  v2 ( )( )  v3 ( )  v4 ( )
R1 Rb
R2 Rb
R3
R4
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A Single Op-Amp Difference
Amplifier
Application of superposition
Inverting configuration
R2
vo1   vI 1
R1
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A Single Op-Amp Difference
Amplifier
Application of superposition.
Noninverting configuration.
R2
R4
vo 2  (1  )(
）vI 2
R1 R4  R3
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Integrators
The inverting configuration with general impedances in the feedback and
the feed-in paths.
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The Inverting Integrators
The Miller or inverting integrator.
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Frequency Response of the
integrator
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The op-amp Differentiator
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The op-amp Differentiator
Frequency response of a differentiator with a time-constant CR.
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Bistable Circuit
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The output signal only has two states: positive
saturation(L+) and negative saturation(L-).
The circuit can remain in either state indefinitely
and move to the other state only when
appropriate triggered.
A positive feedback loop capable of bistable
operation.
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Bistable Circuit
The bistable circuit (positive
feedback loop)
The negative input terminal of the
op amp connected to an input signal
vI.
R1
v  vo
 vo 
R1  R2
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Bistable Circuit
The transfer characteristic of the circuit in
(a) for increasing vI.
Positive saturation L+ and negative
saturation L-
VTH  L 
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Bistable Circuit
The transfer characteristic for
decreasing vI.
VTL  L 
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Bistable Circuit
The complete transfer characteristics.
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A Bistable Circuit with Noninverting
Transfer Characteristics
R2
R1
v  v I
 vo
R1  R2
R1  R2
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A Bistable Circuit with Noninverting
Transfer Characteristics
The transfer characteristic is noninverting.
VTH   L（
 R1 R2）
VTL   L（
 R1 R2）
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Application of Bistable Circuit as a
Comparator
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Comparator is an analog-circuit building block
used in a variety applications.
To detect the level of an input signal relative to a
preset threshold value.
To design A/D converter.
Include single threshold value and two threshold
values.
Hysteresis comparator can reject the
interference.
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Application of Bistable Circuit as a
Comparator
Block diagram representation and transfer characteristic for a comparator having
a reference, or threshold, voltage VR.
Comparator characteristic with hysteresis.
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Application of Bistable Circuit as a
Comparator
Illustrating the use of
hysteresis in the
comparator characteristics
as a means of rejecting
interference.
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Making the Output Level More
Precise
For this circuit L+ = VZ1 + VD and L– = –(VZ2 + VD), where VD is the forward
diode drop.
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Making the Output Level More
Precise
For this circuit L+ = VZ + VD1 + VD2 and L– = –(VZ + VD3 + VD4).
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Generation of Square Waveforms
Connecting a bistable multivibrator with inverting transfer characteristics in a
feedback loop with an RC circuit results in a square-wave generator.
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Generation of Square Waveforms
The circuit obtained when the bistable multivibrator is implemented with the
positive feedback loop circuit.
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Waveforms at various nodes of the
circuit in (b).
This circuit is called an astable
multivibrator.
Time period T = T1+T2
1  （ L L )
T1  RC ln
1 
1  （L L )
T2  RC ln
1 
1 
T  2RC ln
1 
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Generation of Triangle Waveforms
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Generation of Triangle Waveforms
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