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Buffer Op-Amplifier
I/P O/P
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2. CONTENT
 Operational Amplifier
Buffer
Buffered Op-Amp
Basic Buffer Amplifier Circuit
C-MOS Buffers Circuits
Applications
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3. OPERATIONAL AMPLIFIER
An operational Amplifier is a direct Coupled high gain
amplifier usually consisting of one or more differential
amplifiers and usually followed by a level translator and output
stage.
The Operational Amplifier is a versatile device that can be
used to amplify dc as well as input signal and was originally
designed for computing such mathematical functions as
Addition, Subtraction, Multiplication and Integration etc.
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- input
+ input
-
+
+ Vss
- Vss
Output

4. CIRCUIT DIAGRAM OF Op-Amp
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5. INVERTING & NON-INVERTING OP-AMPLIFIER
Vout = - Vin(Rf/Rin) Vout = Vin(1+Rf/Rin)
INVERTING NON-INVERTING
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In this circuit the input signal is
amplified by gain A and also inverted.
In this circuit the input signal is
amplified by gain A and is in phase with
input signal.

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BUFFER
Digital Buffer is nothing a but Even numbers of NOT gates cascade Connected.
I/P O/P
(Same as Input)Invert of I/P
Ideal buffer has a properties :perfect linearity, regardless of signal amplitudes; and instant
output response, regardless of the speed of the input signal
Buffer is device which gives o/p as what ever input is given to it.

7. BUFFER OP-AMPLIFIER
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signal input -
+
+ Vss
Signal Out
- Vss
The op-amp configuration shown at left is a voltage-follower often used as a
buffer amplifier
Output is connected directly to negative input (negative feedback)
Since v+ = v- = vIN, and vOUT = v-, we can see by inspection that the
closed-loop gain Ao = 1
We can obtain the same result by writing
vOUT = A (vIN – vOUT) or
vOUT/vIN = A/(1 + A) = 1 for A >> 1

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• This is a special case of the non-inverting amplifier, which is also called a voltage follower,
(Voltage Series Feed Back Amplifier)with infinite R1 and zero R2.
Hence Av = 1.
• It provides an excellent electrical isolation while maintaining the signal voltage level.
• The “ideal” buffer requires no input current and can drive any desired load resistance
without loss of signal voltage.
• Such a buffer is used in many sensor and data acquisition system applications.
• Used as a "line driver" that transforms a high input impedance (resistance) to a low output
impedance. Can provide substantial current gain.
BUFFER OP-AMPLIFIER
A
High output
impedance
B
Low input
impedance

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0inOOis VAIRIRV:KVL
0inOO VAIRoutV-:KVL
IRV iin:VARIABLEGCONTROLLIN
iOO
is
out
RAR
RV
V
1
1
SOLVING
1
S
out
O
V
V
A
CIRCUIT AND MODEL FOR UNITY GAIN BUFFER

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TRANSFER CURVE
A typical voltage-follower transfer curve is shown for VPOS = +15V and
VNEG = -10V
For vIN between –10 and +15 volts, vOUT = vIN
If vIN exceeds +15V, the output saturates at VPOS
If vIN < -10V, the output saturates at VNEG
Since input current is zero giving zero input power, the voltage follower can
provide a large power gain.

11. BASIC BUFFER CIRCUIT
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Vout(Inverted)
Vout(Non-Inverted)
-
+
+
-
+5
-5
R2
R1
R3
Vin
Vin
Gnd
-5
4
4
7
6
6
5
8
1
5
8
1
2
3
3
2

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C-MOS Buffer Circuit

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C-MOS op-amp with low impedance driving capability

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Buffer StageDifferential Amplifier Stages
Low output resistance C-MOS op-amp Suitable for Driving Resistive Captive Load

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PERFORMANCE OF REAL OP-AMPS
Op-Amp BUFFER GAIN
LM324 0.99999
LMC6492 0.9998
MAX4240 0.99995
PA05 0.999992
REAL Op-Amplifier available in Market

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References
 “Allen and Holberg “ - “CMOS Analog Circuit Design”

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