Legal Metrology • Paper-III
The drain gate capacitance of a junction FET is 2 pF. Assuming a common source voltage gain of 20, what is the input capacitance due to Miller effect?
A)
21 pF
B)
40 pF
C)
42 pF
D)
10 pF
The effective input capacitance is Cgd(1+|Av|) = 2 pF × 21 = 42 pF.
Legal Metrology • Paper-III
Which of the following flip flop cannot be converted to D-type (delay) flip-flop?
A)
S-R flip-flop
B)
J-K flip-flop
C)
Master slave flip-flop
D)
None of these
Correct option: D — None of these. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
The transmission bandwidth is doubled in FM. The SNR is
A)
also doubled
B)
improved four fold
C)
decreased by one fourth
D)
unaffected
A 7-bit PCM stream at 10 kHz has 70 kb/s bit rate; the corresponding baseband bandwidth is about 35 kHz for ideal Nyquist signaling.
Legal Metrology • Paper-III
What is the waveform of the current flowing through the diode in a buck-boost converter
A)
Square wave
B)
Triangular wave
C)
Trapezoidal wave
D)
Sinusoidal wave
Correct option: B — Triangular wave. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
A gate-turn-off (GTO) thyristor
A)
Requires a special turn-off circuit like a thyristor
B)
Can be turned off by removing the gate pulse
C)
Can be turned off by a negative current pulse at the gate
D)
Can be turned off by a positive current pulse at the gate
Correct option: C — Can be turned off by a negative current pulse at the gate. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
For a pulse amplitude modulation (PAM) transmission of voice signal having maximum frequency f_m = 3 KHz. Calculate the transmission bandwidth given sampling frequency f_s = 8 KHZ and pulse duration z = 0.1 T_s
A)
BW >= 20 KHz
B)
BW >= 80 KHz
C)
BW >= 40 KHz
D)
None of these
A 7-bit PCM stream at 10 kHz has 70 kb/s bit rate; the corresponding baseband bandwidth is about 35 kHz for ideal Nyquist signaling.
Legal Metrology • Paper-III
In a 16-bit microprocessor, words are stored in two consecutive memory locations. The entire world can be read in one operations provided the first
A)
word is even
B)
word is odd
C)
memory location is odd
D)
memory address is even
Correct option: D — memory address is even. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
In 8085 microprocessor, the value of the most significant bit of the result following the execution of any arithmetic or Boolean instruction is stored in the
A)
carry status flag
B)
auxiliary carry status flag
C)
sign status flag
D)
zero status flag
TRAP is the highest-priority 8085 interrupt.
Legal Metrology • Paper-III
In a transistor amplifier, the reverse saturation current I0 is
A)
doubled for every 100C rise in temperature
B)
doubled for every 10C rise in temperature
C)
increased linearly with temperature
D)
doubled for every 50C rise in temperature
Correct option: B — doubled for every 10C rise in temperature. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
The main reason for connecting a pulse transformer at a output stage of a thyristor triggering circuit is to
A)
amplify the power of the triggering pulse
B)
provide electrical isolation
C)
reduce the turn on time of the thyristor
D)
avoid spurious triggering of the thyristor due to noise
Correct option: B — provide electrical isolation. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
The instruction INR B is executed if
A)
carry is generated after addition
B)
carry is not generated after addition
D)
zero is not the result of summation
Correct option: B — carry is not generated after addition. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
To overcome slope overload problem, which type of the integrator is used in delta modulation?
A)
Fixed slope integrator
B)
Variable slope integrator
C)
Linear slope integrator
D)
Bipolar integrator
Variable-slope integration increases step size when the input slope is high, reducing slope overload.
Legal Metrology • Paper-III
For a transconductance amplifier, input and output resistance are respectively
A)
infinity and 0
B)
0 and infinity
C)
0 and 0
D)
infinity and infinity
The ideal transconductance amplifier has very high input resistance and very low output resistance.
Legal Metrology • Paper-III
The feedback diodes in a d.c. to a.c. thyristor inverter
A)
freewheeling the load current
B)
provide reverse bias effectively to the thyristors for turn-off
C)
improve the switching properties of the inverter
D)
improve the harmonic distortion of the inverter output current
Correct option: A — freewheeling the load current. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
Turn-on and turn-off times of transistor depend on
A)
Static characteristic
B)
Junction capacitances
C)
Current gain
D)
None of these
Correct option: B — Junction capacitances. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
The digital multiplexer is basically a combination logic circuit to perform the operation
A)
AND-AND
B)
OR-OR
C)
AND-OR
D)
OR-AND
Correct option: D — OR-AND. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
The highest priority of interrupt in 8085 microprocessor system is
A)
RST 7.5
B)
RST 6.5
C)
INTR
D)
TRAP
TRAP is the highest-priority 8085 interrupt.
Legal Metrology • Paper-III
In which of the following codes a binary number Y1 Y2 Y3 is converted by the circuit given below? (Y1 Y2 Y3 -> X1 X2 X3)
A)
Excess-3 code
B)
Gray code
C)
Decimal code
D)
BCD code
Correct option: B — Gray code. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
One of the following methods cannot be used to remove the unwanted sideband in SSB. This is the
A)
filter system
B)
phase-shift method
C)
third method
D)
balanced modulator
With SSB each channel occupies 15 kHz; 14 guard bands add 42 kHz, giving 267 kHz.
Legal Metrology • Paper-III
a.c. voltage regulators are widely used in
A)
traction drives
B)
fan drives
C)
synchronous motor drives
D)
slip power recovery scheme of slip-ring induction motor
Correct option: B — fan drives. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
The waveform A cos(ω t + k cosω t) is
A)
amplitude modulated
B)
frequency modulated
C)
phase modulated
D)
frequency as well as phase modulated
The argument contains a time-varying phase term, so the waveform is phase modulation.
Legal Metrology • Paper-III
The circulating current inductor is required in a dual converter to
A)
Improve power factor
B)
Smoothen the waveform of circulating current
C)
Limit the circulating current
D)
Increase the circulating current
Correct option: C — Limit the circulating current. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
In a transistor, the forward bias across the base emitter junction is kept constant and the reverse bias across the collector base junction is increased. Neglecting the leakage across the collector base junction and the depletion region generation current, the base current will
A)
increase
B)
decrease
C)
remain constant
D)
none of these
Increasing reverse bias widens the collector-base depletion region but ideally leaves base current nearly unchanged under the stated assumptions.
Legal Metrology • Paper-III
In phase controlled rectifiers
A)
the power factor is unaffected by phase control
B)
the power factor worsens if the delay angle is small
C)
the power factor worsens for increasing delay angle
D)
the power factor worsens for large output voltage
Correct option: C — the power factor worsens for increasing delay angle. This matches the standard definition/result for the stated question.
Legal Metrology • Paper-III
Which semiconductor power device out of the following is not a current triggered device?
A)
Thyristor
B)
GTO
C)
Triac
D)
MOSFET
Correct option: D — MOSFET. This matches the standard definition/result for the stated question.
