Digital Electronics MCQs

Digital Electronics MCQs

The following Digital Electronics MCQs have been compiled by our experts through research, in order to test your knowledge of the subject of Digital Electronics. We encourage you to answer these 70+ multiple-choice questions to assess your proficiency.
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1: For a 12-bit ADC, the range of input-voltage is (0 to +10v).The voltage corresponding to LSB is _____.

A.   0

B.   0.0012 v

C.   0.0024v

D.   0.833v<br>

2: The address bus width of a memory of size (1024*8) bit is _____.

A.   8 bits

B.   10 bits

C.   12 bits

D.   16 bits<br>

3: A circuit has an output that is determined by the present input as well as the previous output states. The circuit is known as _____.

A.   a mealy machine

B.   a moore machine

C.   a sequential circuit

D.   None of above<br>

4: To read the RMS value of which of the following waveforms are true RMS reading voltmeters used?

A.   Only the sinusoidal waveform

B.   Only the non-sinusoidal waveform

C.   Both a and b

D.   Only the square waveform<br>


Triggering action can be obtained in a J-K F/F by __________ .

A.   joining J and K points to ground

B.   joining J point to Q and K to ¯Q

C.   joining J and K points to positive supply

D.   adding EX-OR gates at the output


The addition of hexadecimal number DF16 + AC16

A.   11C16

B.   18B16

C.   15B16

D.   19E16


Which family has the fastest speed?

A.   TTL

B.   ECL


D.   DTL


A semi-conductor ROM is basically a ________.

A.   combinational circuit

B.   sequential circuit

C.   set of flip-flops memory elements

D.   None of the above


Race condition occurs in _____.

A.   a combinational circuit

B.   all the digital circuits

C.   a synchronous circuit

D.   an asynchronous circuit


LSI and VLSI devices use the _____ technology.

A.   TTL

B.   ECL

C.   MOS

D.   RCL


If an ADC with 8-bit output gives full-scale deflection for 12v analog-signal, its resolution is _____.

A.   8/12 v

B.   8*12 mv

C.   8/256 v

D.   12/256 v


In sequential circuits, memory elements are _____.

A.   astable

B.   monostable

C.   bistable

D.   tristate flip-flops


A twisted ring counter consisting of 6 F/F will have

A.   6 states

B.   12 states

C.   64 states

D.   128 states


The number of 4-line-to-16-line decoders required to make an 8-line-to-250-line decoder is_____ .

A.   16

B.   17

C.   32

D.   64


In an XNOR gate, input A is high and B is low. The output will _____.

A.   be low

B.   be high

C.   switch between low and high

D.   None of the above


One of the two states of a circuit is stable and the others are quasi-stable. The circuit  is a _____ circuit.

A.   flip-flop

B.   one-shot

C.   bi-stable multivibrator(MVR)

D.   free-running MVR


If inverters are added to the inputs of AND gate, the logic function is _____.

A.   OR

B.   NOR

C.   AND

D.   EX-OR


In a karnaugh map, a quad eliminates _____ variables.

A.   4

B.   2

C.   8

D.   1


In a shift register, complemented output point Ā of the last flip-flop is joined to point J of the first flip-flop while its point K is joined to point A of the last flip-flop. The circuit will work as _____.


A.   a shift count

B.   a shift register

C.   a ring counter

D.   None of the above


A monostable circuit gives a pulse-width output having tp=0.3 Rx.Cx. The device employed is likely to be_____ .

A.   74121

B.   74122

C.   74221

D.   555-timer


9's complement of 56 is _____.

A.   87

B.   49

C.   43

D.   35


A triggerable one-shot monostable MVR _____.

A.   can be triggered in the ON as well as quiescent state

B.   can be triggered only in the quiescent state

C.   can be triggered only in the ON state

D.   does not require any triggering


The time taken by an ADC to perform a conversion is usually referred to as

A.   speed

B.   propogation- delay

C.   response- time


A 4-bit synchronous counter uses flip-flops with the propagation delay time of 25nsec each. The maximum possible time required for the change of state will be _____.

A.   100 nsec

B.   25 nsec

C.   50 nsec

D.   75 nsec


The write-cycle time of a memory is 200 nsec. The maximum rate at which data can be stored is________ 

A.   200 words/sec

B.   5*103 words/sec

C.   5*106 words/sec

D.   5*107 words/sec


A multiplexer having 32 data input lines needs _____ select lines.

A.   5

B.   4

C.   3

D.   6


Which of the following memories uses an index-hole to  provide timing signals?

A.   A magnetic tape

B.   A charged coupled device

C.   A floppy disk

D.   None of the above


Shift-registers most commonly use _____.

A.   D F/F

B.   R-S F/F

C.   J-K F/F

D.   T F/F


A monostable circuit uses a timing register of 10k ohms and a capacitor of 0.1µF capacity respectively. Its pulse-width will be approximately_____ .

A.   0.7 ms

B.   1 ms

C.   0.7 sec

D.   1 sec


Pocket calculators use the_________ system.

A.   BCD

B.   Exess-3

C.   gray code

D.   binary


The minimum number of resistors required in a 4-bit network of weighted resistor type DAC is ______.

A.   4

B.   8

C.   15

D.   16


In the floating point system, the exponent is written in __________ notation.

A.   gray code

B.   hexadecimal

C.   octal

D.   excess-32


The race-around condition occurs in J-K F/F when____________ .

A.   both the inputs are 0

B.   both the inputs are 1

C.   the inputs are complementary

D.   any of the above input combinations is present


The most important advantage of CMOS is its _____.

A.   noise immunity

B.   input impedance

C.   low power consumption

D.   output impedance


In the BCD number system, subtraction is done by the______ method.

A.   10's complement

B.   2's complement

C.   1's complement

D.   9's complement


In a microprocessor, the adder circuit is a part of

A.   instruction register

B.   memory

C.   ROM

D.   ALU


The counting sequence of a uniform counter is 000,001,011,111,110,100.The counter is a _____.

A.   ripple binary counter

B.   combination counter

C.   ring counter

D.   Johnson counter


The comparison time of ADC-0800 is in the range of _____.

A.   a few tens of msec

B.   a few tens of millions of msec

C.   a few milli-secs

D.   a few micro-secs


How many memory locations can 14 address bits access?

A.   64,382

B.   16,384

C.   1024

D.   2,048


A universal register _____.

A.   accepts serial input

B.   accepts parallel input

C.   gives serial and parallel outputs

D.   is capable of all the above


In an IC-555-timer, the load can be connected _____.

A.   only between the output terminal and the ground (GND)

B.   only between the output terminal and the VCC

C.   between the VCC and the GND

D.   between either the output terminal and the GND or between the output terminal and the VCC

A.   simple decade circuitry required

B.   economy in the number of flip flops

C.   high speed of operation

D.   its availability in IC form


Adding inverters to the input of an OR gate produces the _____ logic function.

A.   NOR

B.   AND


D.   EX-OR


Semi-conductor memories are widely used because of their__________ .

A.   small size

B.   low cost.

C.   compatibility with microprocessors

D.   All of the above


A J-K F/F may be obtained by adding__________ 

A.   AND gates to a clocked R-S F/F

B.   OR gates to a D F/F

C.   NAND gates to a T F/F

D.   NAND gates to a R-S F/F


A memory in which the contents get erased when power-failure occurs is called_______ .

A.   RAM



D.   ROM


For a flip-flop with provisions of preset and clear__________.

A.   preset and clear operations are preferred simultaneously

B.   while preseting, clear is disabled

C.   while clearing, preset is disabled

D.   both b and c


One OR gate can work as a _____ comparator

A.   two-bit

B.   three-bit

C.   one-bit

D.   four-bit


In a 4-bit weighted-register DAC, the resistor value corresponding to MSB is 2k ohm. The resistor value corresponding to LSB will be _____.

A.   1 k ohm

B.   2 k ohm

C.   4 k ohm

D.   16 k ohm


A transparent latch consists of a__________  .

A.   T-type F/F

B.   D-type F/F

C.   T or D type F/F

D.   T and d type F/F