Question 1
2N3904
Q1
V1
5TO1CT A A
E
+
60 Hz
C2
100uF
R4
680 C
+
C3
100uF
D
D2
1N4736
R2
680 G
R3
C1
100uF 500
D1
1N4736
F
+
D3
BRIDGE
+
B
C4
R1
100uF 500
H
Q2
2N3906
Fig.1
1.1. From fig.1 draw the waveform signals expected from the points marked A, B, C, D, E,
F, G and H.
(8)
1.2. Explain the reason for each wave shape obtained in Q1.1 above from A and H.
(8)
1.3. What is the name of the circuit in fig.1?
(2)
1.4. What effect would increasing the value of C2 and C3 have on signal in point D?
(2)
1.5. What is the main function of Q1 and Q2?
(2)
1.6. From fig. 1, given voltage at point B as 15Vdc, β =50 of Q1 and Vz = 6.8V at point
Calculate:
1.6.1. The output voltage at point D
(3)
1.6.2. The zener diode current at point C
(15)
[40]
Question 2
Vcc
20V
6k8
220k
Vo
B = 180
Vi
ro =50k
56k
2k2
Fig. 2
2.1. Draw the AC equivalent circuit from the circuit in fig.2.
(10)
2.2. For the circuit in fig.2, calculate:
2.2.1 re.
(15)
2.2.2 VB.
(6)
2.2.3. VC.
(3)
2.2.4. Zi.
(3)
2.2.5. Av.
(3)
[40]
Question 3
Rf
V1
33k
V2
22k
V3
12k
+
Vo
Fig. 3
3.1. For the circuit of Fig.3, Rf= 330 kΩ, V1= +0.2V; V2= -0.5V; V3= +0.8V.
(8)
3.2. List the features of an operational amplifier.
(4)
[12]
Question 4
4.1. Draw and label a circuit diagram of an n-channel depletion type MOSFET.
(8)