ECE 250 Homework #3
Due 3/25/02
Problem 1:
A new diode has been discovered that has the following current-voltage characteristics:
≥
=otherwise
VforV
I
DD
D
0
0
2/5
ρ
where
2/5
50
V
A
µ
ρ
=
Note that the current direction and voltage reference for I
D
and V
D
are the same for a standard semiconductor diode.
+
R
1k
0
+
-
Vin
DC = 12
VoVin
D1
For the circuit above, find numerical values of I
D
and V
D
using:
a) a load line,
b) writing equations and solving with Maple or another equation solver,
c) iteration
Problem 2:
a) For the diode of problem 1, find an equation for the diode resistance that would be used in a piece-wise-linear model of the
diode.
b) Find a numerical value of the diode resistance if the diode voltage is V
D
=5 volts.
c) Create a piece-wise-linear model for this diode and specify numerical values foe the resistor and voltage source.
Problem 3:
The circuit below is a temperature sensor:
+
R1
5000
+5V
+
R2
804.5
+5V
+
C1
1u
+
C2
10u
+
-
V-
V+
U2-0
LM139
At 25 °C the diode voltage is 0.713 volts. At what temperature does the output of the comparator flip.
