Single-Stage Integrated-Circuit Amplifiers

IC Biasing6.3.1 The Basic MOSFET Current Source

2

1

'1 2

1tnGSnD VV

LWkI

RVVII GSDD

REFD

1

2

2

'2 2

1tnGSnDO VV

LWkII

1

2

)/()/(

LWLW

II

REF

O

SATURATION

IC BiasingMOS Current-Steering Circuits

1

22 LW

LWII REF

1

33 LW

LWII REF

4

545 LW

LWII

tnGSSSDD VVVVV 132 ,Effect of Vo on Io

Difference Q2 and Q5

Current Source, Current Sink

IC BiasingBJT Circuits

Current Transfer Ratio

mQQ

II

C

O 1

2

of EBJ of Area of EBJ of Area

Case 1: m = 1

21

121

C

C

REF

O

I

III

C

CREFIII 2

Case 2:

11

mm

II

REF

O

Output Resistance

O

A

O

OO I

VIVR 2

2

111 A

BEOREFO V

VVmmII

IC BiasingBJT Circuits – Current Steering

Effect of Vo on Io

RVVVVI BEEBEECC

REF21

REFII 23

REFII 34

VVV CC 3.0collector

High-Frequency Response The High-Frequency Gain Function

)()( sFAsA HM

gain DCor frequency -low gain, midband :MA

PnPP

ZnZZH sss

ssssF

/1/1/1/1/1/1)(

21

21

S 0, F(s) 1

High-Frequency Response Determining the 3-dB Frequency fH

121

21

/11

/1/1/1/1/1/1)(

PPnPP

ZnZZH ssss

ssssF

A dominant pole exits if the lowest frequency pole is at least two octaves (a factor of 4) away from the nearest pole or zero.

1PH

High-Frequency Response Determining the 3-dB Frequency fH (cont.)

21

21

/1/1/1/1)(

PP

ZZH ss

sssF

2222

22222

21

21

/1/1/1/1

)(PP

ZZjFH

2222

2222

21

21

/1/1/1/1

21

PP

ZZ

HH

HH

22

21

2

22

21

2

22

21

42

221

2

22

21

42

221

2

111

111

/111

/111

PPH

ZZH

PPHPP

H

ZZHZZ

H

22

21

22

21

22111ZZPP

H

High-Frequency Response Determining the 3-dB Frequency fH (cont.)

44

5

104/110/110/1)(

ss

ssFH

High-Frequency Response Using Open-Circuit Time Constants for the

Approximate Determination of fH

nn

nn

H sbsbsbsasasasF

221

221

11)(

PnPP

b

111

211

Difficult to obtain poles and zeros

n

iioiRCb

11

Rio: Seen by Ci when reducing all other capacitance to zero and reducing the input signal to zero

iioi

HP RCb

b 111

111

High-Frequency Response Example 6.6

Small Signal Equivalent Circuit for CS Amplifier

Frequency Response for CS Amplifier032

gd

oxgs

C

WLCC

oxgdgs WLCCC21

Triode

Saturation

High-Frequency Response Example (cont.)

VmAg

pFCC

kRkRkR

m

gdgs

Linsig

/4

1

33.3,420,100 '

H

sigoM

f

VVA /

High-Frequency Response Example (cont.)

)( 'Lm

sigin

in

sig

oM Rg

RRR

VVA

High-Frequency Response Example (cont.)

nsRC

kRRR

gsgsgs

sigings

8.80108.80101

8.80100||420||312

High-Frequency Response Example (cont.)

sigin

xgsin

gs

sig

gsx

RRR

RIVRV

RV

I

||'

'

MRRgRRIVR

RVV

VgI

LmLx

xgd

L

xgsgsmx

16.1''''

'

ns

RC gdgdgd

11601016.1101 612

kHz3.1282

krad/s8061

HH

gdgsH

f

High-Frequency Response Miller’s Theorem

ZKVVI

ZVI 11

1

11

Z

KVVIZKV

ZVI 11

2

1

2

22

00

High-Frequency Response Miller’s Theorem --- Example

?/,1or 1 sigO VVpFMZ

High-Frequency Response Miller’s Theorem --- Example (cont.)

Mk

K

ZZ

kkK

ZZ

99.0

10011

100011

9.91001

10001

2

1

High-Frequency Response Miller’s Theorem --- Example (cont.)

10011

111

10011

1

2

1

sC

K

ZZ

sCK

ZZ

The CS and CE Amplifiers with Active Loads

The CS and CE Amplifiers with Active Loads