Digital Signal Processing Reference
In-Depth Information
i
out
v
GS
=
2.5 V
50
drain
v
out
v
DS
=
v
out
gate
i
D
=
i
out
40
source
V
SS
v
GS
=
2.0 V
30
Saturation
Linear
v
GS
=
1.5 V
20
10
v
GS
=
1.0 V
v
GS
=
0.5 V
0
0.0
0.5
1.0
1.5
2.0
2.5
v
DS
(V)
(a)
v
GS
= −
0.5 V
v
GS
= −
1.0 V
5
−
v
GS
= −
1.5 V
−
15
Saturation
Linear
−
25
v
GS
= −
2.0 V
−
35
V
DD
source
v
DS
=
v
out
−
V
DD
i
D
=
gate
−
45
i
out
v
GS
= −
2.5 V
v
out
drain
i
out
−
55
−
2.5
−
2.0
−
1.5
−
1.0
−
0.5
0.0
v
DS
(V)
(b)
Figure 11-2
Example transmitter pull-up and pull-down
i
D
versus
v
DS
curves:
(a) NMOS (
W
=
222
m,
L
=
1.0
m); (b) PMOS (
W
=
845
m,
L
=
1.0
m).
µ
µ
µ
µ
Figure 11-3b shows the transient response of the inverter when driving a 1-pF
load.
11.2.2 Linear Models
The simplest push-pull transmitter model, shown in Figure 11-4, is the linear
model. Here the transmitter behavior is modeled by a transient voltage source
in series with a resistor (i.e., a Thevenin equivalent circuit). The voltage source
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