chapter 7: building blocks integrated-circuit amplifiers
TRANSCRIPT
Chapter 7: Building Blocks integrated-Circuit Amplifiers
IC Design Philosophy Discrete Circuit v.s. Integrated Circuit Constraints for IC
Large- and moderate-value resistors Large capacitors
Opportunities for IC Constant-current sources Very small capacitors (in the picofarad and fraction of
a picofarad range)
Comparison of the MOSFET and BJT MOSFET
CMOS: the most widely used IC technology for both digital and analog as well as mixed-signal applications
Practical infinite input resistance Can be made quite small Manufacturing process is relatively simple
BJT Higher output currents High reliability under severe environmental
conditions, such as in the automotive industry
6.3 IC Biasing
iD – vDS Characteristics
area gateunit per eCapacitanc :
electrons ofmobility :
)(A/V
region)n (Saturatio 2
1
region) Triode(2
1
2'
2'
2'
ox
n
oxnn
tGSnD
DSDStGSnD
C
Ck
VvL
Wki
vvVvL
Wki
tGD
ttGS
tGSDStGD
ttGS
Vv
VVVv
VvvVv
VVVv
7.0~5.0,
region Saturation
or, ,
7.0~5.0,
:region Triode
6.3 IC BiasingThe Basic MOSFET Current Source
2
1
'1 2
1tnGSnD VV
L
WkI
R
VVII GSDDREFD
1
2
2
'2 2
1tnGSnDO VV
L
WkII
1
2
)/(
)/(
LW
LW
I
I
REF
O
SATURATION
6.3 IC BiasingThe Basic MOSFET Current Source (cont.)
tGSO VVV
Effect of Vo on Io
Effect of Channel Length Modulation
21
2 1A
GSOREFO V
VVI
LW
LWI
Output Resistance
O
A
O
OO I
V
I
VR 2
VA2: Early Voltage Channel Length
6.3 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
6.3 IC BiasingBJT Circuits
Current Transfer Ratio
mQ
Q
I
I
C
O 1
2
of EBJ of Area
of EBJ of Area
Case 1: m = 1
2
1
1
21
C
C
REF
O
I
I
I
I
C
CREF
III 2
Case 2:
1
1
mm
I
I
REF
O
Output Resistance
O
A
O
OO I
V
I
VR 2
2
11
1 A
BEOREFO V
VVmm
II
6.3 IC BiasingBJT Circuits – Current Steering
Effect of Vo on Io
R
VVVVI BEEBEECCREF
21
REFII 23
REFII 34
VVV CC 3.0collector
6.3 IC Biasing6.3.3 BJT Circuits: A Simple Current Source
R
VVI BECCREF
2
1/21 A
BEOREFO V
VVII
REF
AO I
VR
6.4 High-Frequency Response 6.4.1 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
6.4 High-Frequency Response 6.4.2 Determining the 3-dB Frequency fH
121
21
/1
1
/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 facotr of 4) away from the nearest pole or zero.
1PH
6.4 High-Frequency Response 6.4.2 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
2
1
PP
ZZ
HH
HH
22
21
2
22
21
2
22
21
42
221
2
22
21
42
22
1
2
111
111
/11
1
/11
1
PPH
ZZH
PPHPP
H
ZZHZZ
H
22
21
22
21
22111
ZZPPH
6.4 High-Frequency Response 6.4.2 Determining the 3-dB Frequency fH (cont.)
44
5
104/110/1
10/1)(
ss
ssFH
Homework
5.77, 5.112, 4.11, 4.45, 4.74