Differential Amplifier Slide (B)
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1 Differential and Multistage Differential and Multistage Amplifiers Amplifiers ELZ 303 ELZ 303 - Elektronik Elektronik II II Dr. Mehmet Sira Dr. Mehmet SiraçÖzerdem zerdem Elektrik Elektrik Elektronik Elektronik Müh. B h. Bölümü Dicle Dicle Üniversitesi niversitesi Microelectronic Circuits – Fourth Edition Adel S. Sedra, Kenneth C. Smith, 1998 Oxford University Press The basic BJT differential-pair configuration. Microelectronic Circuits - Fifth Edition Sedra/Smith
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Transcript of Differential Amplifier Slide (B)
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1Differential and MultistageDifferential and Multistage
AmplifiersAmplifiers
ELZ 303 ELZ 303 -- ElektronikElektronik IIII
Dr. Mehmet SiraDr. Mehmet Sira zerdemzerdemElektrikElektrik ElektronikElektronik MMh. Bh. BllmmDicle Dicle niversitesiniversitesi
Microelectronic Circuits Fourth Edition
Adel S. Sedra, Kenneth C. Smith, 1998 Oxford University Press
Copyright 2004 by Oxford University Press, Inc.
The basic BJT differential-pair configuration.
Microelectronic Circuits - Fifth Edition Sedra/Smith
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2Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Different modes of operation of the BJT differential pair
The differential pair with a common-mode input signal vCM
Mode 1
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/SmithThe differential pair with a large differential input signal.
Mode 2
Different modes of operation of the BJT differential pair
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3Copyright 2004 by Oxford University Press, Inc.
The differential pair
with a large differential
input signal of polarity
opposite to that in
mode2.
Microelectronic Circuits - Fifth Edition Sedra/Smith
Different modes of operation of the BJT differential pair
Mode 3
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
The differential pair
with a small differential
input signal vi. Note that
we have assumed the
bias current source I to
be ideal (i.e., it has an
infinite output
resistance) and thus I
remains constant with
the change in vCM.
Different modes of operation of the BJT differential pair
Mode 4
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4Copyright 2004 by Oxford University Press, Inc.
Large-Signal Operation of the BJT Differential Pair
Microelectronic Circuits - Fifth Edition Sedra/Smith
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Large-Signal Operation of the BJT Differential Pair
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5Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Large-Signal Operation of the BJT Differential Pair
Copyright 2004 by Oxford University Press, Inc.
Small-Signal Operation of the BJT Differential Amplifier
Microelectronic Circuits - Fifth Edition Sedra/Smith
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6Copyright 2004 by Oxford University Press, Inc.
Small-Signal Operation of the BJT Differential Amplifier
Microelectronic Circuits - Fifth Edition Sedra/Smith
Copyright 2004 by Oxford University Press, Inc.
Small-Signal Operation of the BJT Differential Amplifier
Microelectronic Circuits - Fifth Edition Sedra/Smith
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7Copyright 2004 by Oxford University Press, Inc. 13
An alternative viewpoint
Microelectronic Circuits - Fifth Edition Sedra/Smith
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
An alternative viewpoint with emitter resistances
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8Copyright 2004 by Oxford University Press, Inc. 15
Input Differential Resistance
Microelectronic Circuits - Fifth Edition Sedra/Smith
Copyright 2004 by Oxford University Press, Inc. 16
Differential Voltage Gain
Microelectronic Circuits - Fifth Edition Sedra/Smith
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9Copyright 2004 by Oxford University Press, Inc. 17
Differential Voltage Gain
Microelectronic Circuits - Fifth Edition Sedra/Smith
If the output is taken differentially,
If the output is taken single-endedly,
For the differential amplifier with emitter resistances,
if the output is taken differentially,
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Equivalence of the Differential Amp. to a Common Emitter Amp.
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Copyright 2004 by Oxford University Press, Inc.
Microelectronic Circuits - Fifth Edition Sedra/Smith
The differential half-circuit
Equivalence of the Differential Amp. to a Common Emitter Amp.
Input resistance =
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Equivalence of the Differential Amp. to a Common Emitter Amp.
The differential amplifier fed in a single-ended fashion.
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Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
(a) The differential amplifier fed by a common-mode voltage signal vicm.
(b) Equivalent half-circuits for common-mode calculations.
Common- Mode Gain (Assume that the circuit is perfectly symmetric)
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Common- Mode Gain (Assume that the circuit is perfectly symmetric)
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Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
If the output is taken single endedly, the common mode gain
Since in this case the differential gain is
The common-mode rejection ratio (CMRR)
The common-mode rejection ratio (CMRR) in dB
Common- Mode Gain (Assume that the circuit is perfectly symmetric)
Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Common- Mode Gain (Assume that the circuit is NOT symmetric)
For a mismatch Rc in the collector resistances
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Copyright 2004 by Oxford University Press, Inc.Microelectronic Circuits - Fifth Edition Sedra/Smith
Common- Mode Gain
The circuit is symmetric The circuit is NOT symmetric
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CMRR CMRR
