X489-5 Intro to BJT Differential Amplifiers - UC Berkeley...

Dr. Vincent Chang (張文清)

LectureIntro to BJT Differential Amplifiers

Vincent Chang

Copyright © by Knowledge Master, Inc.

Vincent Chang

Basics

• Large‐signal analysis

• Transfer characteristic

Mode of operation

• Common mode

• Current switching

• Small‐signal

ICMR

• Concept• Hand analysis


Outline


Differential Amplifier


Differential Amplifier

Q1/Q2: Forward-active


I-V Characteristics


TBE VvSC eIi


I-V Characteristics


TBE VvSC eIi

TEB VvvSE eIi )(

11


I-V Characteristics

TBE VvSC eIi


TEB VvvSE eIi )(

11

TEB VvvS

E eIi )(2

2


I-V Characteristics


21 BBD vvv

TEB VvvSE eIi )(

11

TEB VvvS

E eIi )(2

2

TDTBB VvVvv

E

E eeii

)(

2

1 21


I-V Characteristics

TDTBB VvVvv

E

E eeii

)(

2

1 21

QEE Iii 21


I-V Characteristics

TDTBB VvVvv

E

E eeii

)(

2

1 21

QEE Iii 21

QE

EE I

iii )1(

2

12


I-V Characteristics

TD VvQ

E eI

i

12

QE

EE I

iii )1(

2

12

TDTBB VvVvv

E

E eeii

)(

2

1 21

QEE Iii 21


I-V Characteristics

TD VvQ

E eI

i

12

TDTBB VvVvv

E

E eeii

)(

2

1 21

QEE Iii 21

QE

EE I

iii )1(

1

21


I-V Characteristics

TD VvQ

E eI

i

12

TDTBB VvVvv

E

E eeii

)(

2

1 21

QE

EE I

iii )1(

1

21

TD Vve /


I-V Characteristics

TD VvQ

E eI

i

12TD Vv

QE e

Ii

11

QE

EE I

iii )1(

1

21

TD Vve /


Transfer Characteristic

TD VvQ

E eI

i

11 TD VvQ

E eI

i

12

2QI



2QI

TD VvQ

E eI

i

11 TD VvQ

E eI

i

12


Input File

A BJT Differential Pair (ICMR) * circuit description * Vcc1 3 0 DC 10V Vcc2 11 0 DC -10V Vee 5 0 DC -10V Vd 9 0 DC 0V Rd 9 0 1 Vcm 8 0 DC 0V R1 3 2 10k R2 3 6 10k R3 11 10 19.3k EV1 1 8 9 0 0.5 EV2 8 7 9 0 0.5 * BJT model description Q1 2 1 4 npn_transistor Q2 6 7 4 npn_transistor Q3 4 10 5 npn_transistor Q4 10 10 5 npn_transistor .model npn_transistor npn (Is=1.8E-15 Bf=100 Vaf=300V) * analysis requests .OP .DC Vcm -10V +10V 50mV * output requests .probe

.end



98%

2%

TV4



TV4TV6.4

98%

2%

99%

1%

Vincent Chang

Basics



Mode of operation

• Common mode


• Small‐signal

ICMR



Outline


Common-Mode

TD VvQ

E eI

i

11

TD VvQ

E eI

i

12

Common-mode


Common-Mode

2QI

Transfer characteristics Common-mode


Common-Mode

Common-mode


Common-Mode Rejection

2QI

Common-modeTransfer characteristics


Current Switching Mode

Current-switching mode



On Off




2QI

Transfer characteristics Current-switching mode

On Off



2QI

Transfer characteristics Current-switching mode




2QI

Transfer characteristics


Small-Signal Operation

Small-signal operationTransfer characteristics

2QI

Vincent Chang

Basics



Mode of operation

• Common mode


• Small‐signal

ICMR



Outline


Common-Mode Operation

1 2CM

34



1 2CM

34

REF



1 2CM

3

Q

4

REF



1 2CM

3

Q

4

REF CM


Input Common-Mode Range

1 2CM

3

Q

4

REF CM


ICMR

1 2CM

3

Q

4

REF CM


ICMR

1 2CM

3

Q

4

REF CM

1CEv


ICMR

1 2CM

3

Q

4

REF CM


ICMR

1 2CM

3

Q

4

REF CM

3CEv


Maximum Input CM Voltage

1 2

3

Q

4

REF



1 2CM

3

Q

4

REF



1 2CM

3

Q

4

REF

5.5V0.7V0.2V-V5(max) CMv


Minimum Input CM Voltage

1 2CM

3

Q

4

REF



1 2

3

Q

4

REF



1 2CM

3

Q

4

REF



1 2CM

3

Q

4

REF

V1.90.7V0.2VV10(min) CMv



1 2

3

Q

4

REF

V6.5CMv



1 2

3

Q

4

REF

V6.5CMv

V2.0

Q1 saturation



1 2

3

Q

4

REF

V2.9CMv



1 2

3

Q

4

REF

V2.0

Q3 saturation

V2.9CMv


ICMR (SPICE)

2dv

2dv


Simulation Result


Simulation Result

Q3 Saturation

-9.1V0.7V0.2VV10(min) CMv


Simulation Result

Q1/Q2 SaturationQ3 Saturation

5.5V0.7V0.2V-V5(max) CMv


Simulation Result

Q1/Q2 SaturationQ3 Saturation

Q1/Q2/Q3 F-Active

ICMR


WARNING

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X489-5 Intro to BJT Differential Amplifiers - UC Berkeley...

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