ece137A notes 5 source emitter follower - UCSB...Source Follower, Emitter Follower Mark Rodwell,...
Transcript of ece137A notes 5 source emitter follower - UCSB...Source Follower, Emitter Follower Mark Rodwell,...
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
ECE137A, notes set 5:
Source Follower, Emitter Follower
Mark Rodwell, Doluca Family Chair, ECE DepartmentUniversity of California, Santa [email protected]
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Emitter Follower, Source Follower
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Analysis
EER LR
eqLLEECE RRRR ,||||
CER
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Analysis
eqLR ,
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Emitter Follower Voltage Gain
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Impedances in the Emitter Follower
on.degenerati-emitterfor derivedearlier formulas from Follows
CER
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Emitter Follower: Example (1)
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Emitter Follower: Example (2)
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Emitter Follower: Example (3)
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Emitter Follower: Example (4)
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Emitter Follower: Example (5)
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Emitter Follower: Example (6)
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Source Follower Example (1)
regioncurrent -constantin iticscharacters FET Recall gsD VI
( / 2)(1 )
for , where
D v gs th DS
gs th v inj gs g
I K V V V V
V V V K v c W
2( ) (1 )
for , where / 2
D gs th DS
gs th gs g g
I K V V V
V V V K c W L
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Device model: NMOS @ 15nm gate length
plot for 1 micron gate width
ignores VDS term
2
15nm
0.3 V
16mA/V ( /1 m)
2.40mA/V ( /1 m)
75mV
1/ =5V
g
th
g
v g
L
V
K W
K W
V
0.3V
/ 2 0.337VthV V
0.375VthV V
2.4 mA/V/ m
216.0 mA/V / m
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Source Follower Example (3)
1
We've chosen to bias the FET @ 0.4V 0.3V=0.1V and 0.6V.
Velocity-limited: 2.4mA/V ( /1 m)( / 2)(1 ) 1mA.
1mA=2.4mA/V ( /1 m)(0.1 75mV)(1+0.6V/5V) 14.9 m.
Setting 200k
gs th DS
D g gs th DS
g g
g
V V V
I W V V V V
W W
R
2 and 800k provides 0.8V.
0.4V/1.0mA=400 .
g g
ss
R V
R
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Source Follower Example (4)
(1 )
14.9 m 0.6V 2.4mA/V 1
1 m 5V
40mS.
1/ 5V/1mA 5k
m v DS
DS D
g K V
R I
AC small-signal analysis
200k
800k 40010k
10k5.6 mgW
|| || 357
/ / ( 1/ ) 0.93
Leq DS SS L
out in Leq Leq m
R R R R
V V R R g
,
, ,
200k || 800k 160k
/ / ( ) 0.94
in A
in gen in A in A gen
R
V V R R R
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Emitter Followers vs Source Followers
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ECE137A class notes, UCSB, Mark Rodwell, copyright 2019
Source Follower Output Impedance
,More carefully working from the s.s. model shows that (1/ ) ||out T m DSR g R