Electronics MCQs

 Race around problem is unwanted and uncontrollable oscillations occuring in

level trigerred JK flipflop due to a feedback from output to input. It is overcome
by master-slave configuration, edge triggering etc
 Transistor amplifies current
 delay equalization corresponds to adjusting the relative phases of different
frequencies to achieve a constant group delay, using by adding an all-pass filter
in series with an uncompensated filter.
 Weinbridge uses which type of feedback: Positive and Negative
 Relaxation Oscillator: an oscillator in which sharp, sometimes aperiodic
oscillations result from the rapid discharge of a capacitor or inductance.
 Class C power amplifier is a type of amplifier where the active
element (transistor) conduct for less than one half cycle of the input
signal. Less than one half cycle means the conduction angle is less
than 180° and its typical value is 80° to 120°. They are used as RF
amplifiers
 The Class A amplifier is the simplest form of power amplifier
that uses a single switching transistor in the standard common
emitter circuit configuration as seen previously to produce an
inverted output
 A Colpitts Oscillator Uses Tapped Capacitance
 Oscillator circuit converts DC to AC mainly
 Oscillators have positive feedback
 Class A Amplifier: lowest efficiency
 An Amplifier should have stable operation, low noise and high
fidelity
 In physics and engineering the quality factor or Q factoris a
dimensionless parameter that describes how underdamped an
oscillator or resonator is, and characterizes a resonator's bandwidth
relative to its centre frequency. ... Resonators with high quality
factors have low damping, so that they ring or vibrate longer.
 Most stable oscillator: Crystal oscillator
 Pulse transformer uses a ferrite core
 One Bel equals a power ratio of 10
 Decibel is defined in terms of Power ratio
 Band width of an audio amplifier: 20Hz to 20KHz
 Negative feedback in an amplifier: Increases its BW, lowers its lower
3DB frequency, raises its upper 3DB frequency
 Boot strap Darlington amplifier has highest input impedance
 In an FM signal, there are infinite number of side bands
 A delta modulation (DM or Δ-modulation) is an analog-to-digital and digital-to-
analog signal conversion technique used for transmission of voice information where
quality is not of primary importance
To achieve high signal-to-noise ratio, delta modulation must
use oversampling techniques, that is, the analog signal is sampled at a rate several
times higher than the Nyquist rate.
In DM, slope overload distortion can be reduced by increasing the step size
 Typical radar antenna has beam width of: 1 degrees
 In Indian T.V the width of one channel is : 7 MHz
 Interlacing is used in T.V because : it reduces flicker
 As one moves away from transmitter, ground wave eventually
disappears because : Of tilt in wave front
 UHF signals normally propagates by means of : Space wave
 In a low level A.M transmitter, the stage following the modulator
shall be : Linear Amplifier
 The function of pre-emphasis circuit in a communication system is to
boost : higher audio frequencies
 Armstrong modulator generates :FM
 Commonly employed filter in SSB generation is : Mechanical
 Tropospheric scatter is used in the following range : VHF
 The function of padders in radio receiver is to improve : tracking
 The fidelity of a receiver is primarily dependent upon: Audio Amplifier
 The F.M signal is passed through frequency tripler, the resultant
modulation index will change by a factor of :3
 Quantization noise occurs in : PCM
 Blind speed problem in a radar can be effectively overcome by using
:Variable PRF
 If the antenna diameter in a radar system is increased by a factor of
4, the range will increase by a factor of: 4
 To measure high Q inductors, the bridge preferred is: Hay's Bridge
 The voltage gain of an amplifier used with Boolstrap sweep
theoretically shall be: +1
 In AM receiver the oscillator frequency is : Always higher than signal
frequency
 In grid bias modulation system the power needed for modulating
amplifier : Is small as compared to that for plate modulation
 Which of the following is the fastest switching device ?MOSFET
 In a transistor when base-width decreases with increasing collector
to base voltage, this phenomenon is called :Early effect
 Thermal runaway occurs in situations where an increase in temperature changes
the conditions in a way that causes a further increase in temperature, often leading to
a destructive result. It is a kind of uncontrolled positive feedback.
 Tunnelling is often explained in terms of Heisenberg uncertainty principle and
the wave–particle duality of matter.
 The condition for reciprocity of a two port network is :AD-BC =1
 The polar radiation pattern of a loop aerial is: Figure of Eight (8)
 A J-K master slave flip-flop could be converted into a T flip-flop by
making: CLK=0
 The bridge used for measurement of inductance is : Anderson Bridge
 A three and half digit voltmeter could measure a maximum voltage of:
1000 Volts
 Lissajou's figures are used in a CRO while measuring : Frequency
 The type of transmission used for sound in TV transmission is: FM
 The type of transmission used for television in India is :VSB
 A wired AND gate uses : Common Emitter Configuration
 Which of the following is a universal gate: NOR Gate
 The memory unit using only gates is: RAM
 The ladder network used in a D/A converter is: R-2R ladder
 A commercial superheterodyne radio receiver has its intermediate
frequency chosen as: 455 KHz
 An SCR is a device having : Four layers with three junctions
 If the bandwidth of each R F amplifier is 80 KHz the bandwidth of
three such stages cascaded is: 2400 KHz
 The amplifier is which current is proportional to the signal voltage,
independent of source load resistance is called : Transresistance
amplifier
 An emitter follows has: High input inpedance and low output
impedance.
 To eliminate ghosts in the picture: Change the antenna orientation or
location
 An isotropic radiator is a theoretical point source of electromagnetic
or sound waves which radiates the same intensity of radiation in all
directions. It has no preferred direction of radiation. It radiates uniformly
in all directions over a sphere centred on the source.
 The Q factor of a coil is can be given as: wL / R
 VSWR (Voltage Standing Wave Ratio), is a measure of how efficiently
radio-frequency power is transmitted from a power source, through a
transmission line, into a load (for example, from a power amplifier
through a transmission line, to an antenna).
 VSWR = (1+ )/(1- )
 Reflection Coefficient: (ZL –ZS)/ (ZL+ZS)
 Most commonly used materials as photo cathode for the photoelectric
emmission are : Arsenic and Boron
 Current through the ionized gas in gas tube: Usually assumes infinity
 Semi-conductor diode time constant is equal to: The value of
majority carrier life time
 FET is a good signal chopper because : It exhibits no offset voltage at
zero drain current
 In Bipolar Junction transistors, the type of configuration which will
give both voltage gain and current gain is: CE
 The (V^d) - (I^d) characteristics of an FET are similar to that of :
Pentode
 The transformer utilization factor for a bridge rectifier is given as :
0.812
 To increase the input resistance and decrease the output resistance
in negative feedback, the type used is : Voltage Series
 The coupling capacitance of a bipolar transistor amplifier must be:
500 times larger than the FET amplifier
 The loop gain of an amplifier employing feedback (with feedback
ratio of B) is: 1 / B
 The value of a resistor creating thermal noise is doubled. The noise
power generator is therefore: unchanged
 In every practical oscillator the loop gain is: slightly greater than
unity
 Alternatively the characteristic impedance is called : surge
impedance
 For any uniform and symmetrical life the characteristic impedance
is : The geometric mean of the open and short circuited impedance
 The gain bandwidth product of the transistor amplifier is usually
denoted as: f^y
 In crystal oscillators, the valuable properties of a crystal are : High Q
and L/C ratio
 In an RL circuit after a very long time of application of step voltage
the inductance L is represented in its equivalent circuit as : short
circuit
 Thevenin's theorem cannot be applied to a network which contains :
non linear impedances
 The loss produced by the insertion of the network of line is referred
to as the: insertion loss
 A series capacitance used in a filter circuit represents: high pass
 Photoemission multipliers make use of : Secondary emission
 The reflection coefficient on a lossless line with a short circuit load,
is given by: -1
 By passing a triangular wave through a differentiating circuit the
output wave shape is: spikes
 A pulse amplifier is basically an amplifier with : Narrow band
 Linearity of time base waveforms can be improved by using: Larger
time constant
 For harmonic gerneration the amplifier used is: Class C Tuned
Amplifier
 Zener diodes semiconductors are : Heavily doped
 he relative permeability is considered as unity for: Cobalt
 A paralled polarized wave is incident from air to paraffin. If Er for
paraffin is 2, the Brewster angle will be nearly equal to : 55 degress
 Absolute Permeability is equal to: 4 x PI x 10^-7 H/m
 The absorption of radio waves by the atmosphere depends on which
of the following : Their frequency
 Plasma is: A gaseous medium
 Circular polarization is said to take place when: The magnitude is the
same and the phase difference is 90 degs.
 Which of the following is ferromagnetic material : Cobalt
 Response curve of an amplifier is a graph that shows: Variation of
output voltage with frequency
 In FET amplifiers, input is: voltage signal
 Mark the reason for CB configuration having very small input
impedance: That input is applied between emitter and base and
emiiter junction is always forward biased for operation
 The power handling capability of a given transistor, is dependent
upon which of the following: Maximum junction temperature and
expected ambient temperature.
 H-parameters of a transistor: Are dependent upon collector current
 High frequency response of a transformer coupled amplifier is
generally limited by : Transformer's leakage inductance and
distributed capacitance
 Low frequency response of a transformer coupled amplifier is limited
by: Transformer's primary inductance
 In a voltage series feedback: Output and input resistances are
reduced
 Which coupling produces the minimum interference with frequency
response : Direct Coupling