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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 2 Examinations 2007/
School: School of Electrical & Electronic Engineering
Programme Title: Bachelor of Engineering (Honours) in Electronic Engineering
Programme Code: EELXE_8_Y
Module Title: Analogue Electronics
Module Code: ELTR 6001
External Examiner(s): Prof. G. Hurley Dr. S. Foley Internal Examiner(s): Dr. P O’Connor
Instructions: Answer Q1 (40 Marks) and any other 2 Questions (30 Marks each). Maximum available marks is 100.
Duration: 2 Hours
Sitting: Summer 2008
Requirements for this examination:
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you are attempting the correct examination paper. If in doubt please contact an Invigilator.
Q1. (a) Draw a circuit diagram for a filtered bridge rectifier and explain the operation of each section using waveform diagrams. [8 marks]
(b) For the four circuits shown in Fig. Q1(b), sketch the expected output waveform, if the input in each case is 30 Vp-p sinusoidal waveform.
[12 marks]
(c) Sketch a gain/frequency characteristic for a typical RC-coupled common- emitter transistor amplifier. Explain the reasons for the fall-off in the curve, label the 3-dB points, and briefly explain their significance. [10 marks]
(d) Design a practical common-emitter (C-E) amplifier using a voltage divider circuit, in which Vcc = 24V, VQ = 12V and I (^) Q = 1mA. The circuit should operate satisfactorily using Si transistors whose values of hFE= β range from 50 to 200. [10 marks]
Q2. (a) Explain why stabilisation of the operating point (Q-point) is necessary in a transistor amplifier and how it is achieved in the circuit shown in Fig. Q2. Discuss the factors affecting the choice of resistors R 1 , R 2 and RE.
[8 marks]
(b) Calculate the Q-point coordinates (i.e. V (^) CEQ, I (^) CQ) and the overall voltage gain ( s
out V
V (^) ) for the common-emitter amplifier in Fig. Q2, if the driving
source voltage (Vs ) for the amplifier has a 600 Ω series resistance (assume
β DC = 75, β ac = 70). [14 marks]
(c) If an emitter bypass capacitor (CE) was introduced across RE, demonstrate by using calculations, the effect this would have on the voltage gain. [8 marks]
Fig. Q1(b)(i)
input 1k ouput
Fig. Q1(b)(ii)
input 1k ouput
Fig. Q1(b)(iv)
input ouput 10 V
Fig. Q1(b)(iii)
input ouput
1k
10 V o
o
o
o
o
o
o
o
o
o
o
o
o
1k
o
o
o
+Vcc
Vin
R R
R
1
2
C
C (^1)
C (^3)
RE
= 3.3k
12k = 1k
47k
= 18V
Vout
RL = 10k
Fig. Q
N-Channel Junction
Vdd = 24V
V
VO
r
s
s
R R
R
R
R
D
L
s
C
s
50 K
2.2M
510K
1 K
1.7 K
20 K
Fig. Q
