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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ANSWER: Crystal controlled oscillator




(2) Barkhausen criterion for oscillator stability is

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

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ANSWER: - Aβ = 1




(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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ANSWER: Around 3




(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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ANSWER: High Q




(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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ANSWER: Reverse dc control voltage




(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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ANSWER: Dc control voltage




(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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ANSWER: Two oscillators with slightly different oscillating frequencies




(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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ANSWER: High impedance switches and frequency dividers




(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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ANSWER: Oscillator circuit can be operated in class A condition for better waveshape




(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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ANSWER: RC circuits




(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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ANSWER: Reduction in transistor gain




(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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ANSWER: A Schmitt trigger




(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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ANSWER: Use of a tuned circuit




(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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ANSWER: A higher positive dc control voltage will make the oscillator frequency higher




(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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ANSWER: Unchanged




(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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ANSWER: 0.1 μH




(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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ANSWER: I-C applications




(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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ANSWER: 100 MHz




(19) Find the odd one out

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

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ANSWER: Stellite




(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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ANSWER: Square wave




(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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ANSWER: 0.4375




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

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

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ANSWER: 4563




(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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ANSWER: 81.707




(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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ANSWER: 1000




(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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ANSWER: OR gate




(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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ANSWER: Common emitter amplifier




(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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ANSWER: OR gate




(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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ANSWER: Four




(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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ANSWER: Shift Registers




(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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ANSWER: 140 mA




(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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ANSWER: 110 100 100 100




(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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ANSWER: 10 TTL




(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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ANSWER: 0




(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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ANSWER: Voltage mode, positive logic




(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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ANSWER: Weight




(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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ANSWER: Integrated circuits




(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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ANSWER: A square on a karnaugh map




(39) FORTRAN variables may not be declared as

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

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ANSWER: Triple precision




(40) A 48 K computer memory contains

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

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ANSWER: 49152 bytes



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  • RE: Oscillators, Digital circuits - Electronics Engineering test questions -divya gupta (09/08/14)
  • sir/mam
    plz send me this type of question ,which is asked in GATE,PSU,IES exams.And mostly asked in placement interview.