UNIT.
ELECTRONICS
CODE; ENG /OS/PO/CR/04/6
End of Term 11 cat 1 and 2, July 2024
Time: 2 Hours
PC KINYANJUI TECHNICAL TRAINING INSTITUTE
ELECTRICAL & ELECTRONIC ENGINEERING DEPARTMENT
QUALIFICATIONS: ELECTRICAL ENGINEEERING LEVEL 6
LEVEL 6
TERM 1I
INSTRUCTIONS TO CANDIDATES
1. This paper consists of TWO sections CAT1 and CAT 2
2. Answer all questions in booklets provided
3. Maximum marks for each question are as indicated.
4. Candidates should answer the questions in English.
Section 1 CAT 1 50 marks
1. With aid of a diagram explain the parts of transistor and their uses ( 2 marks)
2. 2.Draw the symbols of NPN and PNP transistors and mention different transistor currents
3. and voltages indicating the polarity (4 marks )
4. The current gain of a transistor in CE mode (β) is 49. Calculate its CB current gain (α). Also find the
collector current when the emitter current is 3mA. (6markrs)
5. Explain the operation of NPN transistor with aid of a diagram (4 marks)
6. Calculate IC and IE for a transistor that has α dc=0.98 and IB=100µA. Find the value of βdc of the
transistor .(6 marks)
7. Briefly explain the operation of a transistor. (4 marks)
8. Give the relation between α and β. (4 marks)
9. Determine VCB in the transistor circuit shown in Fig. 10 (i). The transistor is of silicon and has β =
150. (4marks )
10.
11. Find the value of β if (i) α = 0.9 (ii) α = 0.98 (iii) α = 0.99 (3marks )
12. Calculate IE in a transistor for which β = 50 and IB = 20 μA. (3marks)
13. Find the α rating of the transistor shown in Fig. 4. Hence determine the value of I C using both α and β
rating of the transistor. (4marks)
14.
15. The collector leakage current in a transistor is 300 μA in CE arrangement. If now the transistor is
connected in CB arrangement, what will be the leakage current? Given that β = 120 (2marks)
16. Explain why an ordinary junction transistor is called bipolar? (2marks)
UNIT. ELECTRONICS
CODE; ENG /OS/PO/CR/04/6
End of Term 11 cat 1 and 2, July 2024
Time: 2 Hours
PC KINYANJUI TECHNICAL TRAINING INSTITUTE
ELECTRICAL & ELECTRONIC ENGINEERING DEPARTMENT
QUALIFICATIONS: ELECTRICAL ENGINEEERING LEVEL 6
LEVEL 6
TERM 1I
INSTRUCTIONS TO CANDIDATES
1. This paper consists of TWO sections CAT1 and CAT 2
Section 2 CAT2 80 marks
1. Why transistor is called current controlled device? (3marks)
2. Why silicon type transistors are more often used than Germanium type? (3marks)
3. Why the width of the base region of a transistor is kept very small as compared to other regions?
(4marks)
4. Give the comparison between three transistor configurations .(10 marks)
Properties Common Base Common Common
Emitter Collector
Input
Impedance
Output
Impedance
Voltage Gain
Current Gain
Power Gain
5. Mention the applications of CE, CB and CC configurations of BJT’s. (6marks)
6. Which of the BJT configuration is suitable for impedance matching application and why?(4marks)
7. What are the requirements of a transistor biasing network? (3marks)
8. What are the types of biasing? (3marks)
9. A transistor has α = 0.99. if it is connected in CE mode. what would be a change in collector current
for a change of 10μA in base current? (4marks)
10. In a transistor connected in CE mode if the base currents are changed from 20μA to 30μAat fixed
VCE =7.5v, the collector current changes from 2.2 mA to 3.2mA. find β. At operating point. (6marks)
11. The transistor below has β.= 100, VBE = 0.7v. Determine the region of operation VCE and value of
Ib, Ic and VCB for RB is equal to
12. (i)500kΩ
13. (ii)120kΩ (6marks)
14.
15. A transistor in CE mode is connected with a resistance 5kΩ and power supply of 5v in the collector
circuit. if α = 0.998 and the voltage drop across the 5kΩ is 5v. find base current (6marks)
16. The transistor below has β =100 find the values of Ib and Ie and VCE (6marks)
17.
18. For the transistor below β= 50, vbe =0.8v find the limiting value of Rb for which the transistor is
driven. (6marks)
