EMLAB
1
Chapter 6. Building blocks of inte-grated-circuit amplifiers
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2
1. IC design philosophy2. Basic gain cell3. Cascode amplifier4. IC biasing5. Current mirror6. Useful transistor pairings
Contents
EMLAB
31. IC design philosophy
• Large R, L, C should be avoided → minimize chip area• DC supply voltage in the range of 1V.
EMLAB
4Exemplary chip layout-TL431
EMLAB
5Ideal biasing (Rbias→∞)
이상적인 바이어스 회로인 경우 active load 의 저항이 무한대 .
R
EMLAB
62. Basic gain cell
저항보다 트랜지스터 쓰는 것이 면적에서 유리 .
DSV
DI
DI
≡
Active loaded CS amplifier
02
1slope
r
or
EMLAB
7
1or
2or
)||( 21 oomi
oV rrgA
Voltage gain of current-source load
SR
LR
EMLAB
8Increasing the gain of the basic cell
Current buffer
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9
)1( omSoo rgRrR
om
L
mom
Loin rg
R
grg
RrR
1
1
1
Input/output impedance of a common gate amplifier
6.3 Cascode amplifier
L
Lin
RD
C
RB
A
I
VR
1
1
S
So CRA
DRB
I
VR
2
2
1011
1
om
o
omcg
rg
r
rgDC
BA
Common gate 로 연결된 drain 에서 본 source impedance 는 원래보다 (1+gmro) 배 커짐 .
Common gate 로 연결된 source 에서 본 source impedance 는 원래보다 (1+gmro) 배 작아짐 .
MOS cascode
EMLAB
10MOS cascode
Common source
Common gate
CS 증폭기에 CG 증폭기 연결하면 output impedance 는 원래보다 (1+gmro) 배 커짐 .
2d
imG
outR
To load
EMLAB
11
001
)1(1
)1(
1
00
1
1
1
)1(
1
1011
1
00
11
22
2212
112211
122
2
112211
22
2
22111
om
omoo
omomom
mom
o
omomom
om
o
ommomtotal
rg
rgrr
rgrgrg
grg
r
rgrgrg
rg
r
rggrgDC
BA
Common source Common gate
122122212221 )1( oomoomooomooS
Sout rrgrrgrrrgrr
A
B
CRA
DRBR
)||(/1/11
/
/11
1
2Loutm
Lout
m
LL
in
out RRGRR
G
RBA
B
RB
AV
VA
11222
2211
1
2
)1(
111m
oomo
omom
Lin
outm g
rrgr
rgrg
BBARV
IiG
221221 BIIARVBIAVV L
)0( SR
)0( LR
Calculation of cascode design parameters (ABCD)
CS, CG 두 형태의 ABCD 파라미터로 계산
Trans-conductance :
Output impedance :
Voltage gain :
EMLAB
12Trans-conductance (Gm) of a cascode amplifier
SR
)(/
1)(
112121
22
22222
oimogsogsimo
gso
mogsogsmo
igrrgi
rgirgi
1
2
112
12
112
112
22
11211
22
1
11)(
1
m
o
oom
mo
oom
i
oi
imoo
moo
oomoimo
omo
g
rr
rg
grr
rgi
G
grr
gir
rrgigr
rgi
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13
1112
2222
)(
)(
oooimogs
ogsogsmo
rirgi
rgi
)0( i
12212221
1222
)(
)1(
oomoomooout
ooomoo
rrgrrgrrR
irrgr
Output impedance of a cascode amplifier
EMLAB
14Cascode amplifier with a cascode current-source load
])[(||])[(
)||(
4331221
1
oomoomm
oponmi
o
rrgrrgg
RRgA
EMLAB
153.5 Double cascoding
Figure 7.15 Double cascoding.Figure 7.16 The folded cascode.
(VDD 를 낮추기 위해 )
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16
Input/output impedance of a common base amplifier
L
Lin
RD
C
RB
A
I
VR
1
1
e
eo CRA
DRB
I
VR
2
2
Common base 로 연결된 collector 에서 본 source impedance 는 원래보다 (1+gmro) 배 커짐 .
Common base 로 연결된 emitter 에서 본 source impedance 는 원래보다 (1+gmro) 배 작아짐 .
)1(//1
1
)1(
1
omo
o
omcbrgrrr
r
rgDC
BA
)||)(1( eomoo RrrgrR
om
Le
L
e
o
Lo
Lom
o
L
o
in rg
Rr
rR
rr
Rr
Rrg
rr
r
Rr
R
1111
1
1
3.7 BJT cascode
mg
or
E
B C
r
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17
out
Common emitter
Common base 2c
imG
outR
To load
CE 증폭기에 CB 증폭기 연결하면 output impedance 는 원래보다 (1+gm2ro2) 배 커짐 .
BJT cascode
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18
)||)(()||)(1( 212221222 rrrgrrrgrA
B
CRA
DRBR oomoomo
S
Sout
)||(/1/11
/
/11
1
2Loutm
Lout
m
LL
in
out RRGRR
G
RBA
B
RB
AV
VA
121222
21221
1
2
)||)(1(
)||)(1(11m
oomo
oomm
Lin
outm g
rrrgr
rrrgg
BRBV
IiG
221221 BIIRVBIAVV L
)0( SR
)0( LR
Trans-conductance :
Output impedance :
Voltage gain :
2221
2
1211
2221
2
1211
22
22222
2
111
111
22
1||
1
)||(
1
1||
1
)||(
1
)1(
1
)1(//1
111
11
)1(
1
omo
o
o
omo
o
mom
om
omo
o
o
mom
omcas
rgrr
r
rr
rgrr
r
grrg
rg
rgrrr
r
r
grgrgDC
BA
Calculation of cascode design parameters (ABCD)
CE, CB 두 형태의 ABCD 파라미터로 계산
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19
Figure 6.19 A BJT cascode amplifier with a cascode current source.
EMLAB
204. IC biasing
2
11 )(
2
1tnGSnD VV
L
WkI
R
VVII GSDD
REFD
1
2
22 )(
2
1tnGSnDO VV
L
WkII
1
2
)/(
)/(
LW
LW
I
I
REF
O
MOS current mirror
GSV
DI
tnV DDV
R
VDD
VDD 와 R 을 이용하여 Q1 의 VDS 를 고정하여 Q2 를 전류원으로 만들 수 있다 . VO 가 변해도 전류는 고정 .
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21
om
rg
||1
1
1
||1
om
rg
gsgsmg
or
D
ds
gsgsmg
or
G
ds ormg
1
Small signal equivalent circuit
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22
Figure 6.23 Basic MOSFET current mirror. Figure 6.24 Output characteristic of the current source
21
2 1)/(
)/(
A
GSOREFO V
VVI
LW
LWI
)( tnGSOVO VVVV
EMLAB
23Current-steering circuits
1
22 )/(
)/(
LW
LWII REF
1
343 )/(
)/(
LW
LWIII REF
4
543 )/(
)/(
LW
LWII
EMLAB
244.3 BJT current mirror
CI
CCCREF IIII
21/2
2
1
1
21
C
C
REF
O
I
I
I
I
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25
2r11 || oe rr
2
22 mg
2or
D
ce
mg
or
G
ce ormg
1
r r orer
Small signal equivalent circuit
EMLAB
26Simple BJT current mirror
A
BEOREFO V
VVII 1
)/2(1
R
VVI BECC
REF
Figure 6.31 Generation of a number of constant currents of various magnitudes.
R
VVVVI BEEBEECC
REF21
EMLAB
275. Improved current-mirror circuits
233 )( oomo rrgR
Cascode current-mirror
Current mirror 의 output impedance 는 증가하나 VO 의 최소 출력 전압이 높아서 voltage range 가 좁아지는 것은 단점이다 .
tnOVO VVV 2
GSV
GSV
tnOVGS VVV 222
GSV
11
||1
om
rg
44
||1
om
rg
전압 고정
전압 고정
EMLAB
28BJT mirror with base-current compensation
22 /21
1
)/(21
1
REF
O
I
I
)1(
21
CREF II
R
VVVI BEBECC
REF31
EMLAB
29Wilson current-mirror
2/21
1
)1(2
11
)1(2
1
REF
O
I
I
Q3 collector 전류 증가→ Q1 의 베이스 전압 증가 → Q2 의 collector 전류 증가 → Q3 의 베이스 전류 감소 (negative feed-back 임 ).
EMLAB
30
3r
3
33 mg
3or
x
2 12 || err22 mg
2or
xi
33332
3333
3
3
2
12333 1
/1)(
om
mom
m
eomxx rg
rgrg
rg
rrgi
3
3
2
13
3123
2
223
3
12
233
12
2 1/11
||
11
1
1
||||
rg
r
rrrr
r
rgi
rrrir
rri
m
e
e
o
omx
ex
ex
32
33
3
2
222
33
2222222
3
332
11
1
1)1(
rgr
r
rg
r
rrgrg
r
m
o
om
oomom
33333
32
1
33
2
1
2
1
11
/1oom
m
e
om
x
xo rrrg
rgr
rg
iR
Output impedance B
C
EC
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31
3gs33 gsmg
3or
x
2gs 11
||1
om
rg
22 gsmg 2or
xi
2333 )( gsogsmxx rgi
22222223 )1( gsomgsogsmgs rgrg
1
12 ||
1o
mxgs r
gi
xom
omgsomgs irg
rgrg
1
1222223 ||
1)1()1(
xom
xom
omomxo
gsgsomoxx
irg
irg
rgrgir
rgri
11
11
22333
23333
||1
||1
)1(
23311
22333
11)1( oom
mmomomo
x
xo rrg
ggrgrgr
iR
Wilson MOS mirror
EMLAB
32Widlar current source
S
OTBE
S
REFTBE I
IVV
I
IVV ln,ln 21
EOO
REFTBEBE RI
I
IVVV
ln21
REFTOTO
REFTEO IVIV
I
IVRI lnlnln
OI
V
REFI
EORI
oEmoEomoout rrRgrrRrgrR )]||(1[)||(
Q1, Q2 의 전류 비율이 크고 작은 저항으로 해결하기 위함 .
O
REFT I
IV ln
EMLAB
33Example 6.6
The two circuits for generating a constant current IO = 10 μA shown in Fig. 7.37 oper-ate from a 10-V supply. Determine the values of the required resistors, assuming that VBE is 0.7 V at a current of 1 mA and neglecting the effect of finite β.
][94201.0
58.010
][58.0][1
][10ln7.0
1
1
kR
VmA
AVV TBE
][5.11
][10
][1ln025.01010ln
][3.9001.0
7.010][1
3
36
3
2
kR
A
mAR
I
IVRI
kRmAI
O
REFTO
REF
EMLAB
346. Some useful transistor pairingsFigure 6.38 (a) CC–CE amplifier; (b) CD–CS amplifier; (c) CD–CE amplifier.01
1bi
11 bi
1or
E
B C
1r
2or
E
B C
2r
))(1( 11 inein RrR
2rRin
in
in
out
1gs11 gsmg
1or
E
B C
2gs22 gsmg
2or
E
B C
in
LR LR
2bi
22 bi
1112 ogsmgs rg
)||( 222 Logsmo Rrg
211
21
11 gs
omgsgsin rg
Lm
om
Lom
in
o Rg
rg
Rrg2
11
22
11
)||(
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35
212121221
2
1
21
1
2
1
21
1
2
222
222
111
11
1
11
)1(
111
)1(
1
11
11
1
11
11
)1(
1
)1(
1
1
omomo
e
mo
ee
mo
e
o
o
mom
o
eo
e
rgrgr
r
gr
rr
gr
r
r
r
grg
r
rr
r
DC
BA
)||)(1(11
111
11
1111
)1(1111
)1(1
1111
2111
21
2111
212
22111
1
22121
22
1
21
1
rrr
rr
rrrr
rg
grrr
Rrrg
Rrr
grr
RD
C
RB
AZ o
o
oe
om
moee
Loom
Lo
e
mo
e
L
Lin
)||()||(
)||(
111111111
122
211
21
22111
2
22
2
111
2Lom
oe
o
Looee
m
Lo
m
oee
m
L
Rrgrrr
rr
Rrrrrr
g
Rrg
rrr
g
RB
AA
CC–CE amplifier
111 mg
1or
E
B C
1r
222 mg
2or
E
B C
2r
Common collector
Common emitter
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36
][5.222 krRin 111 )1( rrRin
]/[155)160(99.098.0
)||( 2212
2
1
VV
RrgrR
R
RR
RA Lom
ein
in
insig
in
b
o
Example 6.7Find Rin, overall voltage gain. (I1=I2=1 [mA], β = 100 , Rsig = 4 kΩ, RL = 4 kΩ, ignore ro)
][5.2],[25
],/[4021
krrg
r
VmAV
Igg
em
e
T
Cmm
][2555.2525.2)1( 111 kkkrrRin
EMLAB
37
01.00
251
)1(
1
)1(
1
1
o
eo
e
CC
r
rr
r
DC
BA
01.00
25011
11
o
mom
CE
r
grgDC
BA
410.10
25.250
01.00
250
01.00
251
totalDC
BA
]/[4.158
425.25
0
11VV
kRB
AA
L
in
out
),( 21 oo rr
1V
2V
2I1I
DC
BA
2
2
1
1
I
V
DC
BA
I
V
L
in
out
RB
AV
VA
1
1
2
22 IRV L
21221 VR
BAVBIAVV
L
EMLAB
38Darlington configuration
21
111 mg
1or
E
B C
1r
222 mg
2or
E
B C
2r
))(1( 22 Eein RrR
))(1( 11 inein RrR
LR
높은 β 값을 갖는 BJT 역할함 .
Q1 의 β 값이 DC bias current I 에 의존 .
EMLAB
39
111 mg
1or
E
B C
1r
222 mg
2or
E
B C
2r
)1(
1
)1(
1
)1()1(
1
)1(
11
)1(
1
)1(1
)1(11
)1(
1
)1(
1
)1()1(
1
)1(
11
)1(
1
)1(1
)1(11
)1(
1
)1(
1
1
)1(
1
)1(
1
1
2111
2
2212
2
11
2
12
1
1
22
1
2
2
1
1
2111
2
2212
2
11
2
12
1
1
22
1
2
2
1
1
222
22
2
111
11
1
o
e
oo
e
o
ee
o
e
o
e
o
e
o
e
o
e
oo
e
o
ee
o
e
o
e
o
e
o
e
o
eo
e
o
eo
e
r
r
rr
r
r
rr
r
r
r
r
r
r
r
r
r
r
rr
r
r
rr
r
r
r
r
r
r
r
r
r
rr
r
r
rr
r
DC
BA
LR
EMLAB
40
Lo
e
oo
e
o
L
ee
o
e
o
e
o
e
o
e
L
Lin
Rrr
rrr
r
Rr
rrr
rr
rr
rr
RD
C
RB
AZ
1)1(
1)1(
1)1()1(
1)1(
11
)1(1
1)1(
1)1(
11
2111
2
2212
2
11
2
12
1
1
22
1
2
2
1
1
CC–CC amplifier
)]||()[1(||)1(
)]||()[1(
)]||()[1()]||()[1()1(
)]||()[1(
)]||()[1()1(
11)1(
1111
11)1(
111111
)1(
222111
1222
2221122211
1222
11222111
22221
2
2222112
11
Loeoe
oLoe
LoeoeLoeo
oLoe
eoLoeeo
LoLoeo
e
LoLoeoee
e
Rrrrr
rRrr
RrrrrRrrr
rRrr
rrRrrrr
RrRrrrr
RrRrrrrr
r
)1)(1()]||()[1(
)||)(1(1)1(
11)||)(1(
)/()||)(1)(1(
1111
)1)(1(
11
)1)(1(
11
)1)(1(
1111
)1)(1(
)1(1
)1(1
)1()1(1
)1(1
1)1(
1
11
21221
1221
2121
22
2221
2212
21
2
21
21
2
21
2
21
1
2
1
2
221
2
21
1
2
2221
2
21
2111
2
2212
2
11
Loeo
oLo
L
oo
Lo
LLo
oLoL
e
L
oo
L
oe
L
o
ooo
L
e
L
ooL
ooeo
o
eL
oo
e
o
Li
Rrrr
rRr
R
rrrrRr
rRRr
rRrrrR
rR
rr
rR
rr
rR
rr
rr
rr
rR
rR
rr
rr
Rrrrr
r
rr
Rrr
rr
DCRA
EMLAB
41
1
)||(
)||(
)||)(1(||
)||)(1(||
)||)(1()||)(1(
)||)(1(
)||)(1(1
)||)(1(
)||)(1(||11
1
1)1(
1)1(
11
11
22
2
22211
2221
22222211
1
22
2221
11
22
22
1
2
2
1
1
2
12
1
1
22
1
2
2
1
1
Loe
Lo
Looe
Loo
LoLooo
e
Lo
Loo
ee
Lo
Lo
e
Lo
e
o
e
L
ee
o
e
o
e
o
e
o
e
L
Rrr
Rr
Rrrrr
Rrrr
RrrRrrrrr
Rr
Rrrrr
r
Rr
Rrr
Rrr
rr
Rr
rrr
rr
rr
rr
RB
AA
EMLAB
42CC–CB amplifier
EMLAB
43
1
11 mg
1or
E
B
C
1er
2
22 mg
2or
E
BC
2er
Example 6.8