Download Analog Electronics

ANALOG ELECTRONICS
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VYAS PARAG (130430109035)
MALUKA KRUNAL (130430109029)
PANDYA NANDISH (130430109034)
PATEL MEETKUMAR (130430109040)
MER VISHAL (130430109031)
■ Applications of OP-AMP
■ Summing Amplifier
■ Average Amplifier
■ Integrating Amplifier
■ Differential Amplifier
Op-amp Application
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Introduction
Op-amps are used in many different applications. We
will discuss the operation of the fundamental op-amp
applications. Keep in mind that the basic operation
and characteristics of the op-amps do not change —
the only thing that changes is how we use them
Summing Amplifier
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The inverting amplifier
can accept two or
more inputs and
produce a weighted
sum.
Using the same
reasoning as with the
inverting amplifier, that
V ≈ 0.
The sum of the
currents through R1,
R2,…,Rn is:
Vn
V1 V2
iin  
 ... 
R1 R2
Rn
Summing Amplifier
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The op-amp adjusts
itself to draw iin
through Rf (iin = if).
if
iin
Vout  iin R f
Rf
Rf 
 Rf

 V1
 V2
 ...  VN
R2
RN 
 R1
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The output will thus be the sum of V1,V2,…,Vn,
weighted by the gain factors, Rf/R1 , Rf/R2 ….., Rf/Rn
respectively.
Summing Amplifier
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Special Cases for this Circuit:
1. If R1 = R2 =……= R then:
Vout  
Rf
R1
VIN1  VIN 2  .....  VINn 
if
iin
Summing Amplifier
2. If R1 = R2 = … = R and VIN1, VIN2, … are either 0V
(digital “0”) or 5V (digital “1”) then the output
voltage is now proportional to the number of
(digital) 1’s input.
if
iin
Differencing Amplifier
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This circuit produces an output which is
proportional to the difference between the two
inputs
R
vout 
f
R1
v1  v 2 
Differencing Amplifier
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The circuit is linear so we can look at the output due
to each input individually and then add them
(superposition theorem)
Differencing Amplifier
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Set v1 to zero. The output due to v2 is the same as
the inverting amplifier, so
v out  2  
Rf
R1
v2
Differencing Amplifier
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The signal to the non-inverting output, is reduced by
the voltage divider:
v in 
Rf
R1  R f
v1
Differencing Amplifier
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The output due to this is then that for a noninverting amplifier:
vout 1
Rf

  1 
R1


v in

Differencing Amplifier
v in 
vout 1
Rf
R1  R f
Rf

  1 
R1

v1

v in

Rf

v out 1   1 
R1

 Rf 
v1
vout 1  
 R1 
 R f

R R
f
 1

v1


Differencing Amplifier
 Rf
vout 1  
 R1



v1

Thus the output is:
v out  2  
vout  vout 1  vout 2 
Rf
R1
Rf
R1
v2
v1  v2 
Thus the amplifier subtracts the inputs and amplifies
their difference.
Integrator
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The basic integrator is easily identified by the
capacitor in the feedback loop.
A constant input voltage yields a ramp output. The
input resistor and the capacitor form an RC circuit.
Integrator
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The slope of the ramp is determined by the RC time
constant.
The integrator can be used to change a square wave
input into a triangular wave output.
Integrator
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The capacitive impedance:
1
1
Xc 

jC sC
Integrator
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The input current:I  Vin   Vout   Vout   sCVout
Ri
Xc
1 /sC
Integrator
Vout
1

Vin
sCRi
Op-Amp Integrator
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The op-amp provides a constant-current source for
the capacitor, causing it to charge at a linear rate.
Differentiator
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Differentiator – A circuit whose output is
proportional to the rate of change of its input
signal
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Summary
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The summing amplifier’s output is the sum of the inputs.
An averaging amplifier yields an output that is the average
of all the inputs.
Integrators change a constant voltage input to a sloped
output.
Differentiators change a sloping input into a step voltage
proportional to the rate of change.
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