The document discusses buffer amplifiers and operational amplifiers. It defines a buffer as a device that provides an output that is identical to its input. An operational amplifier configured as a voltage follower acts as a buffer amplifier, with a gain of exactly 1. This allows the buffer to provide electrical isolation while maintaining the signal voltage level. Real op-amps can achieve gains very close to 1, making them suitable for use as buffer amplifiers. Applications of buffer amplifiers include driving resistive loads and use in sensor and data acquisition systems.

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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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3
- 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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