3 mos current mirrors - uc berkeley extension online …ucberkeleyext.com/documents/ic/x489/3_mos...

Dr. Vincent Chang (張文清)

Lecture MOS Current Mirrors

Vincent Chang

Copyright © by Knowledge Master, Inc.

Vincent Chang

Intro

• Basic circuit• DC & AC

Cascode

• Intuitive analysis

•MOS diode

Output resistance

• Evolution • Summary: BJT vs. MOS


Outline


Review

BJT current mirror


BJT vs. MOS

MOS current mirrorBJT current mirror


DC Analysis

Q2 saturation


DC Analysis

Q2 saturation2

1 )(21

tGSnREF VVkI

22 )(

21

tGSnO VVkI


Current Transfer Ratio

1

2

n

n

REF

O

kk

II

Q2 saturation2

1 )(21

tGSnREF VVkI

22 )(

21

tGSnO VVkI


Current Transfer Ratio

1

2

)()(

LWLW

II

REF

O

Q2 saturation

1

2

n

n

REF

O

kk

II


Output Characteristic


Output Resistance

2oO

Oout r

IVR

Vincent Chang

Intro


Cascode


•MOS diode

Output resistance



Outline


MOS Current Mirror

Basic current mirror


MOS Current Mirror

Cascode current mirror Basic current mirror


Output Resistance

42 ooout rrR


Output Resistance (Wrong!)

42 ooout rrR


Cascode Current Mirror

MOS diode


Review: BJT Diode


MOS Diode

Vincent Chang

Intro


Cascode


•MOS diode

Output resistance



Outline


Output Resistance


Output Resistance

244 )1( ooout rrR


Yosemite National Park, California


Review—Output Resistance

BJT

)||()1( Eoout RrrR


Review

BJT

)||()1( Eoout RrrR

omrg


Summary—Output Resistance

BJT MOS

)||()1( Eoout RrrR Soout RrR )1( r

omrg omrg


Resistance Reflection Rule (Take Note)

MOS

Soout RrR )1(

omrg

1244 )1( ooout rrR


Output Resistance

Soout RrR )1(

244 )1( ooout rrR


Output Resistance

244 )1( ooout rrR

Soout RrR )1(


Output Resistance

24424 oomooout rrgrrR

244 )1( ooout rrR

Soout RrR )1(


Output Resistance

24424 oomooout rrgrrR

)2( omoout rgrR

ooo rrr 42


Summary—Output Resistance (Take Note)

BJT MOS

)||()1( Eoout RrrR Soout RrR )1( r

omrg omrg


SPICE Simulation


SPICE Input File

Output Characteristics of MOS Cascode Current Mirror Circuit* circuit description *Vdd 1 0 DC 15VVo 4 0 DC 5VIref 1 2 DC 1mA* MOSFET model description M1 3 3 0 0 nmosfet L=10u W=100uM2 5 3 0 0 nmosfet L=10u W=100uM3 2 2 3 0 nmosfet L=10u W=100uM4 4 2 5 0 nmosfet L=10u W=100u.model nmosfet nmos (kp=20u Vto=+1V lambda=0.02)* analysis requests.OP.DC Vo 0V 15V 10mV* output requests.probe.end



M4 saturationM4 triode


Mode Analysis


Mode Analysis of M2



Mode Analysis of M4



Mode Analysis

M4 saturation

M2 triode

M4 triode

M2 saturation


Mode Analysis

M4 saturation

M2 triode

M4 triode

M2 saturation

M4 triode

M2 sat


WARNING

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3 mos current mirrors - uc berkeley extension online …ucberkeleyext.com/documents/ic/x489/3_mos...

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