T1
2 kohm
Vdd = 16 V
100 kohm
Vdd = 16 V
500 kohm
2 kohm
Vdd = 20V
500 ohms
T1
1 Mohm
4 Mohm
Vdd = 20V
0
2
4
6
8
10
12
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Drain Current (mA)
GatetoSource Voltage (V)
ECE 255
ELECTRONIC ANALYSIS AND DESIGN
Fall 2009
Homework 6 Solutions
Problem 1
Let V
DD
= 16 V and R
1
= 500 k
Ω
in the bias circuit shown below.
The MOSFET is described by the
nonlinear relationship
2
GS
D
V
I
30
1
m A
3
= 
+
.
Find I
D
and V
DS
.
(
29
GS
G
100
V
V
16 V
2.667V
100
500
=
=

= 
+
But V
T
= 3 V; consequently, the MOSFET is cutoff.
Therefore, the operating point is I
D
= 0 and V
DS
= 16 V.
Problem 2
The FET shown in the figure below happens to be modeled more closely by the nonlinear trigonometric
relationship
D
GS
I
9
9cos
V
m A
3
3
π
π
=


, than by a parabola when operating in the Beyond
PinchOff region.
Find the operating point.
(
29
G
1
V
20 V
4V
1
4
=
=
+
GS
G
D
SS
D
V
V
I
R
4
.5I
=

×
=

(where I
D
is in mA)
or
(
29
GS
D
GS
4
V
I
8
2V
m A
.5

=
=

also
D
GS
I
9
9cos
V
m A
3
3
π
π
=


You have two equations in two unknowns (I
D
and V
GS
) – solve – either by trialanderror or
graphically (as shown below).
V
GS
= 1.9502 V
and
I
D
= 4.10 mA
(
D
GS
I
8
2V
m A
=

D
GS
I
9
9cos
V
mA
3
3
π
π
=


This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
R
2
Vs
Problem 3
Any linear 2port circuit can be char
by the following pair of equations:
V
1
=
h
11
I
1
+
h
12
V
2
I
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '08
 Staff
 Transistor, Trigraph, The Circuit, Vgs, Zin

Click to edit the document details