Tài liệu Circuits & Electronics P22 pdf

6.002 Fall 2000 Lecture
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6.002
CIRCUITS
AND
ELECTRONICS
Energy and Power
6.002 Fall 2000 Lecture
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Why worry about energy?
small batteries
Æ good
Today:

How long will the battery last?
in standby mode
in active use

Will the chip overheat and self-destruct?
-
6.002 Fall 2000 Lecture
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Look at energy dissipation in
MOSFET gates
Let us determine
standby power
active use power
Let’s work out a few related examples first.

C: wiring capacitance and
C
GS
of following gate
V
S
C
R
O
v
+
–
I
v
+
–
6.002 Fall 2000 Lecture
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Example 1:
Power
Energy dissipated in time T
R
V
VIP
2
==
VITE =
+
–

R
I
V
+
–
V
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Example 1:
for our gate
ONL
S
RR
V
P
+
=
2
0=P
O
v
S
V
ON
R
L
R
I
v

high
S
V
ON
R
L
R
O
v
I
v
low
6.002 Fall 2000 Lecture
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Example 2:
Consider
Find energy dissipated in each cycle.
Find average power .
P
S
V
+
–
1
R
C
2
R
1

S
2
S
openS
closedS
2
1
t
closedS
open
S
2
1
1
T
2
T
T