Oscillators, Digital circuits - Electronics Engineering test questions

Oscillators, Digital circuits - Electronics Engineering test questions

(1) The most stable oscillator among the following given options is

(A) Crystal controlled oscillator
(B) Colpitts oscillator
(C) Hartley oscillator
(D) Wein bridge oscillator

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(2) Barkhausen criterion for oscillator stability is

(A) Aβ = 0
(B) - Aβ = 1
(C) Aβ = 1
(D) A = 1/√β

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(3) Oscillation will not be produced in an RC phase shift oscillator until and unless the voltage gain of its internal amplifier is

(A) Around 3
(B) 1
(C) < 1
(D) > 29

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(4) For good stability, the tuned circuit should have

(A) Low L
(B) Low C
(C) High Q
(D) Low R

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(5) In a voltage controlled oscillator, the varacter needs

(A) Audio signal below 1000 Hz
(B) Forward bias
(C) Parallel capacitance more than 5 μF
(D) Reverse dc control voltage

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(6) In a PLL circuit the phase comparator is used to provide

(A) Dc control voltage
(B) Double crystal oscillator signal
(C) RF output with audio modulation
(D) One- half the crystal oscillator frequency

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(7) A Beat frequency oscillator consists of

(A) A low Q inductor
(B) A high Q inductor
(C) Two oscillators with slightly different oscillating frequencies
(D) A tube and RC network

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(8) Blocking oscillators are used as

(A) Low impedance switches
(B) High impedance switches and frequency dividers
(C) Abrupt pulse generators
(D) All of the above

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(9) Which of the following statement is true for oscillator circuit?

(A) Oscillator circuit can be operated in class A condition for better waveshape
(B) Oscillator circuit can be operated in class A condition to give sinusoidal waveform
(C) Oscillator circuit can be operated in class A condition to give distorted waveform
(D) Oscillator circuit cannot be operated in class A condition

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(10) A phase shift oscillator consists of a number of

(A) RLC circuits
(B) LC circuits
(C) RL circuits
(D) RC circuits

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(11) An oscillator can stop working when there is

(A) Elimination of triggered pulses
(B) An increase in transistor gain
(C) Reduction in transistor gain
(D) None of the above

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(12) For converting a sine wave to a square wave the circuit that can be used is

(A) RLC circuit
(B) A Schmitt trigger
(C) A astable multivibrator
(D) A bistable multivibrator

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(13) The step that will help in stabilizing the frequency of an oscillator is

(A) Use of a tuned circuit
(B) Controlling the gain
(C) Use of automatic biasing
(D) None of the above

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(14) For voltage controlled oscillator

(A) Dc control voltage will not change the oscillator frequency
(B) A higher positive dc control voltage will make the oscillator frequency lower
(C) A higher positive dc control voltage will make the oscillator frequency higher
(D) None of the above is valid

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(15) When L is doubled and C is halved, the frequency is

(A) One quarter
(B) Doubled
(C) Halved
(D) Unchanged

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(16) For an oscillator frequency of 110.7 MHz, C = 20 pF. L =

(A) 0.1 μH
(B) 1 μH
(C) 0.01 μH
(D) 0.001 μH

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(17) Surface Acoustic wave oscillators are suitable for

(A) Non-sinusoidal waveforms
(B) I-C applications
(C) Low power oscillations
(D) Low frequency oscillations

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(18) A tuned circuit used in colpitts oscillator is shown in figure. The frequency of oscillations will be



(A) 10 MHz
(B) 1 MHz
(C) 100 MHz
(D) 0.1 MHz

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(19) Find the odd one out

(A) Stellite
(B) Quartz
(C) Rochelle salt
(D) Tourmaline

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(20) A digital signal is provided by

(A) Gradual turning of a potentiometer
(B) Slow change in the value of a resistor
(C) Sine wave
(D) Square wave

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(21) The decimal form of binary 0.0111 is

(A) 0.4375
(B) 0.1600
(C) 0.2728
(D) 0.7964

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(22) 9’s complement of decimal number 5436 will be

(A) 4563
(B) 4655
(C) 4653
(D) 4356

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(23) Decimal 18.293 when converted into 10’s complement will become

(A) 81.077
(B) 81.777
(C) 81.707
(D) 81.700

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(24) How many different BCD numbers can be stored in a register containing 12 switches using an 8,4,2,1 code

(A) 100
(B) 1000
(C) 999
(D) 99

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(26) A + B = Y is the Boolean function for

(A) NAND gate
(B) AND gate
(C) OR gate
(D) NOR gate

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(27) ____________is an inverter

(A) Common base amplifier
(B) Common emitter amplifier
(C) Common collector amplifier
(D) All of the above

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(28) The gate that corresponds to the action of parallel switches is

(A) NAND gate
(B) AND gate
(C) NOR gate
(D) OR gate

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(29) To a logic gate with a fan in factor of four the number of inputs that can be supplied is

(A) Four
(B) Three
(C) Two
(D) Eight

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(30) The op.amp is used in

(A) Shift Registers
(B) D/A converters
(C) A/D converters
(D) None of the above

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(31) When the number 8 is on an LED display, the current drawn will be

(A) 140 µA
(B) 140 nA
(C) 140 mA
(D) None of the above

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(32) Decimal number 937 in gray code is written as

(A) 100 100 100 100
(B) 110 100 100 111
(C) 111 111 111 111
(D) 110 100 100 100

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(33) The fan out of a 7400 NAND gate is

(A) 2 TTL
(B) 10 TTL
(C) 8 TTL
(D) 5 TTL
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(34) The inputs of a 7420 four input NAND gate are 3.9 V, 4.0 V, 4.1 V and 3.7 V. The output logic level will be

(A) 1
(B) 0
(C) 15.7
(D) 4.1

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(35) For a gate circuit, the binary logic levels are 1 = +12 V and 0 =0 V.The type of logic used is

(A) Current mode, positive logic
(B) Current mode, negative logic
(C) Voltage mode, positive logic
(D) Voltage mode, negative logic

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(36) To refer to the positional value of a digit the term used is

(A) Multiplier
(B) Decimal
(C) Radix
(D) Weight

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(37) Monolithic technology is widely used in the manufacture of

(A) Integrated circuits
(B) Antenna
(C) Transistors
(D) All of the above

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(38) A minterm is

(A) Always smaller than the maxterm
(B) A square on a karnaugh map
(C) A prime implicant
(D) The minimum term in a Boolean function

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(39) FORTRAN variables may not be declared as

(A) Triple precision
(B) Integer
(C) Real
(D) Complex

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(40) A 48 K computer memory contains

(A) 47256 bytes
(B) 48512 bytes
(C) 49152 bytes
(D) 48000 bytes

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