ECE 250 Homework #2
Due 3/18/02
Problem 1:
A silicon PN junction diode has a donor doping concentration of N
d
=10
17
/cm
3
and an acceptor doping concentration of
N
a
=10
16
/cm
3
. Plot the built-in barrier potential for this diode for temperatures from –55 °C to 125 °C. Should the y-axis be
plotted in a log scale? Why or why not?
Problem 2:
Repeat problem 1 for germanium.
Problem 3:
For the diode of problem 1, Cjo is measured to be 2 pF. Generate a plot of the junction capacitance Cj versus reverse diode
voltage, V
R
, for
V10VmV1
R
≤≤
. The x-axis should be a log scale for this plot.
Problem 4:
a) By hand, plot Vo(t) and Vin(t) for the circuits below. Let Vin be a +/- 15 Volt triangle wave.
b) By hand, plot the transfer curve Vo versus Vin for the circuits below.
You may assume that the diodes are ideal.
Circuit 1
D2
-
+
Vin
+
R2
10k
+
R1
4k
Vo
D1
+
R3
6k
Circuit 2
Vo
D1
-
+
Vin
+
R1
4k
+
R3
6k
