we can analyze the small-signal voltage gain of the 741 op-amp …rhabash/elg4135l18.pdf ·...
TRANSCRIPT
1
Small-Signal Analysis of the 741We can analyze the small-signal voltage gain of the 741 op-amp by dividing it into its basic circuits and using results previously obtained
in the DC analysis.
2
The Input Stage
Ω==
+=
Ω===
=
M 2.1 200,NFor )1(4
k 63.2µA 5.9mV 25
4
idRerNidR
ITVer
eriv
ei
ββ
3
The load circuit of the input stage
erivoi
mG
eioi
21
2α
α
==
=
4
Finding Ro5 and Ro6
Ω==Ω=Ω=
=====+=
M 7.6// M 2.18 ;M 10.5
A 9.5 V; 50 ;kΩ 63.2
)//(1[
164
064
ooo
o
AAo
eE
Emoo
RRRRR
IV/IVrrR
rRgrR
µ
π
5
Example: Determine the small-signal differential voltage gain of the 741 op-amp input stage. Assume transistor gain of β = 200 and Early
voltages of VA = 50 V.
6
mA/V 365.0026.00095.06
6
k 5470095.0
026.0200
66
M 4.07)(201)(18.63292
kΩ 3290158.0
026.0200
1616
kΩ 6.18)]1.0)(201(63.9//[50
kΩ 63.954.0
026.0200
1717
]8)1(17//[9
)1(162
]6//2(61[61
)2//1//4()2//1//4(
===
Ω=×
==
Ω=+=
=×
==
=+=
=×
==
++=++=
+=
=−=
TVCI
mg
CITVr
iRCITVr
ERCITVr
RrRERERriRrRmgoractR
iRacRorTVCQI
iRacRormgdA
βπ
βπ
βπ
βπ
βππ
7
636)07.4//18.7//26.5)(026.05.9(
MΩ 26.50095.050
44
M 7.1847)]0.365(1//55.26[11
MΩ 26.50095.050
66
−=−=
===
Ω=+=
===
dA
CIAVor
actRCIAVor
8
The Gain (Second) Stage)])(1//()[1( 81717916162 RrRrR eei ++++= ββ
BoBo
oBoo
rRRRR
1313
17132 kΩ 81)//(=
==
9
The Output Stage
2023samin
14satmax
EBEBtCEEEo
BECECo
VVVVvVVCVv
+++−=−−=
10
11
Circuit for Finding the Output Resistance Rout
12
Gain, Frequency Response, and Slew Rate of the 741
V/V 243147
))(//( 3221211
22
22
=+
−−
=
o
outL
Lvoomom
o
o
i
o
i
i
i
o
ARR
RGRGRRG
vv
vv
vv
vv
13
Frequency Response
Hz 1.42
1M 5.2)MΩ 4//MΩ 7.6()2//1(
)21(
==
Ω===
+=
tRinCpf
iRoRtRACCinC
π
14
A Simple Model of the 741
CCmGt
CCjmGjA
CsCmG
siVsoVsA
1;1)(
1)()(
)(
==
==
ωω
ω
15
Slew Rate
CCISR
tCCItov
2
2)(
=
=