ECED3201: Introduction to Electronics - Fall 2020
Dalhousie University, Department of Electrical and computer Engineering
Practice Problems #4
Problem 1
In the circuit below assume Q1 has  = 100 and IS = 6.95×10-16A, VT=25mV, for Q1.
+5V
+5V
RC=
200
R1 =
5kW
Q1
RE =
300W
R2 =
5kW
Fig. 1
Determine the value of collector current IC and verify the operating region of Q1.
Problem 2
Analyze the circuit below when RC changes from 0 to 1.8kW. RB=20.8kW and =100. Assume VEB1= 0.7V.
VCC= 2V
RB
Q1
V1= 1V
RC
Fig. 2
Problem 3
Determined the voltages at the nodes B1, C1, E1, B2, C2, E2 and the currents IE1, IB1, IC1, IE2, IB2, and IC2.
Assume VBE1= VBE2 = 0.7V and 1=2=100.
1
+6V
+6V
+6V
RC1=
1.2kW
RB1 =
3kW
RC2 =
1kW
C1
B1
C2
Q1
E1
B2
Q2
E2
RE1 =
1kW
RB2 =
3kW
RE2 =
2.5kW
Fig. 3
Problem 4
In this circuit below, assume VEB1 = VBE2 = 0.7V, and 1=2=100.
Determine the currents IE1, IB1, IC1, IE2, IB2, and IC2 and verify the region of operation of Q1 and Q2.
+5V
+5V
9.1kW
5.1kW
Q1
Q2
100kW
9.1kW
-5V
4.3kW
-5V
Problem 5
In the circuit shown below, the transistor has VEB=0.7V and =30.
a) Find the values of VB, VE, and VC.
b) If RB is raised to 270 kW, what voltages result?
c) With RB = 270kW, what value of  would return the voltages of the values first calculated?
2
+9V
RE
2.7kW
E
B
Q
C
RC
RB
27kW
2.7kW
-9V
Fig. 5
3