EC 402
Analog Electronics Circuits
Lecture #23
Differential Amplifiers
IInnstructor:
Chiranjib Goswami, PhD
asansol engineering college
asansol
EC 402 , Lec# 23, June
2022
© Chiranjib
Goswami
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Analog Electronics Circuits Differential amplifier, Slides of Analog Electronics
Differential amplifier: Basic structure and principle of operation, calculation of differential gain
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EC 402
Analog Electronics Circuits
Lecture # 23 Differential Amplifiers
IInnstructor:
Chiranjib Goswami, PhD
asansol engineering college asansol EC
Lec#
June © Chiranjib
Agend
a
Differential Amplifiers
Differential Mode Operation
Common Mode Operation
Use of Constant Current Source 2
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Basic Internal Arrangement of an Op-Amp. EC
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Single-Ended Input & Double-Ended (Differential) Input 5
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Common Mode Operation
This operating feature is referred to as common-mode rejection.
7
Ideally, the two inputs are equally
amplified, and since they result in
opposite-polarity signals at the
output, these signals cancel, resulting
in 0-V output.
Practically, a small output signal will
result.
- (^) Common-Mode Rejection
Noise (any unwanted input signal) is generally common to
both inputs, the differential connection tends to provide
attenuation of this unwanted input while providing an
amplified output of the difference signal applied to the inputs.
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Differential Amplifier Circuit
Input signal combinations:
Double-ended : If two opposite-polarity input signals are applied.
Single-ended : If an input signal is applied to either input with the
other input connected to ground.
Common-mode : If the same input is applied to both inputs.
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Problem 10
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Calculate the dc voltages and currents in the circuit of Fig.
Solution 11
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The collector current is then
resulting in a collector voltage of
AC Operation..
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AC Operation..
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Single-Ended AC Voltage Gain
AC Operation...
The single-ended voltage gain magnitude at either collector
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AC
Operation..
H.W. Derive the Ad equation
2- Double-Ended AC Voltage Gain
A similar analysis can be used to show that for the condition of signals
applied to both inputs, the differential voltage gain magnitude is:
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EC
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Problem EC
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