ESTCN 1 ALTERNAT NG CLRPENT THECAY
ine he seectuty
r n i racricaA crentaticr 1 euer atarca starce rc mcetarce
144
orsicer tte cirit atrV f arait Acnsist of 15 0 resisor ard a 200 F
A r Carslate the fcilcwirg datafor circuit B
131 The irrert thrau cárcuit B 5)
132 Tre ogonerts of ingetancein circauít B
[15]
GUESTION 2: POWER SUPPLIES
Ervan treturctan ctthe foilowing crnprertsin a poner supply
1
21.1
212 Voitays rerglator (1)
Tho foking values f the RC--fliter circut are known
VaAAS, = 08 V: Cz = 100 uF
V 1 4 7; l , = 1A R= 10 0 R = 1 K
adf Hzfrfull wavs roctifer circuit.
Catulats tris tolcwig
(3)
22.1 Ths output DC voitage
factor (5)
222 The percertaye utput ripple
overcurrent
with th ad of a rneat labelled circuit diagrarn how an (5)
Shn, supply
coinGcted in apower [15]
protoction is
wUESTION 3: AMPLIFIERS
3.1 Complete the following sentences by writing only the missing word or words
next to the question number (3.1.1-3.1.3) in the ANSWERBOOK.
The fixed-bias circuit produces a (3.1.1) ... as amplifier, but experiences
problems with the (3.1.2) ... of bias stability. In any amplifier the (3.1.3).. will
vary with the change in temperature.
(3 x 1)
3.2 iven are the values from the common emitter amplifier:
lc= 10 mA: CE = 15 uF and RE = 450 Q
Calculate:
3.2.1 The supply voltage
(4)
3.2.2 The minimum input frequency for the amplifier
(3)
3 Choose a term from COLUMN B that matches a
Write only the letter (A-E) next to the question description in COLUMN A.
ANSWERBOOK. number (3.3.1-3.3.5) in the
COLUMN A
3.3.1 Active filter
COLUMN B
A T-circuit are connected on an
input
3.3.2 Low-pass filter B it can be tuned
in or adjusted easily
3.3.3 High-pass filter C T-circuits are connected on
feedback
3.3.4 Band-pass filter D uses inductors in an input
3.3.5 Band-reject filter E uses capacitors in an input
(5x 1) (5)
51
QUESTION 4: INTEGRATED CIRCUIT AND TRANSDUCERS
when
4.1 List FOUR precautionary measures that can be taken into consideration
handling CMOS chips or MOSFET transistors. (4)
if the
4.2 If a potentiometer has a value of 3%, what will be the supply voltage be
(3)
voltage drop across to adjacent turns is 15 mV.
be used.
4.3 List TWOways in which a Wheatstone bridge thermistor can (2)
be connected in a
4.4 Draw the circuit diagram to show how a strain should
Wheatstone bridge, as well as the differential amplifier
that observes the
displacement equivalent signal. (6)
[15]
QUESTION 5: ELECTRONIC POWERCONTROL
be switched off. (3)
5.1 Name THREE methods how an SCR can
loop control system. (7)
5.2 Briefly describe the operation principle of a closed [10]
QUESTION 6: MEASURING INSTRUMENT
to
an analogue voltage, but converts it
6.1 List FOUR Voltmeters that measure (4)
digital signals.
A/D-converter uses an integrator. An integrating wave form is
slope Vu.
6.2 The dual
slopes and two-time interval which are proportional to
obtained with two
A/D- converter:
function of the following terms on a dual slope
Give the
6.2.1 Switch actuator
6.2.2 Flip-flop
6.2.3 Counter
6.2.4 Gate
6.2.5 Display unit (6)
(6x 1)
[10]
Clock pulse generator
6.2.6
QUESTION 7: OSCILLATORS
(2)
7.1 Name TWO requirements of oscillation.
TRUE or FALSE by writing only
7.2 Indicate whether the following statements are (7.2.1-7.2.3) in the ANSWER
the question number
ue or False' next to
BOOK.
consists of four identical
R-C sections
shift network
7.2.1 The R-C phase feedback line.
and is connected in the
controls
Colpitts oscillators C1 controls frequency and C2
7.2.2 In the
amplitude of the oscillations.
L, with acentre tap and the
7.2.3 In the Hartley oscillators, the inductor
capacitor C1 form the resonant circuit. (3 x 1) (3)
voltage converter. (5)
7.3 Draw a neat and labelled diagram of the DC-DC [10]
LIQUID-CRYSTAL DISPLAY
QUESTION 8:
active matrix. (6)
8.1 Distinguish between passive and
(4)
8.2 Name FOURapplications of LCDs. [10]
TOTAL: 100
QUESTION 1: ALTERNATING CURRENT THEORY
1.1 Define the selectivity. (1)
1.2 DTaw a y'apical representation of every reactance, resistance and impedance (3)
of a series RLC versus frequency.
3
16A
250V
50Hz A B
Consider the circuit above, if circuit A consist of 15 Q resistor
and a 200 uF
capacitor. Calculate the following data for circuit B:
The current through circuitB (5)
1.3.1
(6)
1.3.2 The components of impedance in circuit B [15]
QUESTION 2: POWER SUPPLIES
2.1 Explain the function of the following components in
a pOwer supply:
(1)
2.1.1 n-filter circuit
(1)
2.1.2 Voltage regulator
RC-TT-filter circuit are known:
2.2 The following values of the C2 =100 uF
10 Q; RL = 1kQ; VR(RMS) = 0.8 V:
Voc = 14V: loc =1A; R=rectifier
wave circuit.
and f= 50 Hz for full
Calculate the following:
(3)
2.2.1 The output DC voltage
(5)
percentage output ripple factor
2.2.2 The
neat labelled circuit diagram how an overcurrent (5)
2.3 Show, with the aid of a power supply. [15]
connected in a
is
protection
