EEE393 Basic Electrical Engineering
Homework 4
1. For the two diode circuits below, find VZ for (VA=0V, VB=0V), (VA=5V, VB=0V), and
(VA=5V, VB=5V). Assume VON=0.7V for the diodes. For each case find V1 and V2.
2. In the diode circuit below, find for which values of VS are the diodes ON and OFF. Draw
the output VL for a period of input VS, if VS=10⋅cos(ωt).
3. The four resistor biasing ciruit is a widely used configuration for transistor biasing
(setting the DC operating point, or the Q-point – Vout,Q, IC,Q – so that the transistor is in
the desired operating region with desired margins). We will design a biasing circuit
through the following steps.
a. What is the highest and lowest possible value for
IC (i.e. saturation and cut-off)? A useful
approximation is that IC ≈ IE (i.e. IB is negligable
with respect to IC). Accordingly, what is the
highest and lowest possible value for Vout
(Vout,min and Vout,max)?
(In terms of unknown resistances).
VS RL
+
VL
−
+ V1
−
+
−
5V +
−
+
V2
−
A
+5 V
Z A
B
R
−
V1 +
−
V2 +
Z A
B
R
+ V2
−
+ V1
−
Vout
R1 RC
RE
R2
+ 12V
−
B
I
C
I
E
I
1
I
2
I
B
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