Digital Electronics Test

Digital Electronics Test

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

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

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

Pocket calculators use the ___________ system.

a. BCD

b. Exess-3

c. gray code

d. binary

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

a. 5

b. 4

c. 3

d. 6

In a kamaugh map, a quad eliminates ___________ variables.

a. 4

b. 2

c. 8

d. 1

The boolean expression xy + xz + xyz (xy + z) is equal to ___________

a. 0

b. x

c. y

d. 1

e. x(y+z)

In BCD to 7 segment decoder/driver, the input is 1000. The segments which will be lit are ___________.

a. none

b. all segments

c. 2 segments

d. 4 segments

Race condition occurs in ___________.

a. a combinational circuit

b. all the digital circuits

c. a synchronous circuit

d. an asynchronous circuit

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

a. RAM

b. EAROM

c. PROM

d. ROM

In a shift register, complemented output point A 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

The design of a sequential circuit requires the use of ___________.

a. K-maps

b. state table/state diagram

c. Quine McCluskey method

d. None of the above

Semi-conductor memories are widely used because of their ___________.

a. small size

b. low cost

c. compatibility with microprocessors

d. All of the above

A1 us pulse can be converted into a 1 ms pulse by using a ___________ multivibrator(MVR).

a. monostable

b. Schmrtt-trigger

c. latch

d. free-running MVR

Shift-registers most commonly use ___________.

a. DF/F

b. R-S F/F

c. J-K F/F

d. T F/F

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

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

If in a clocked R-S Flip Flop, point R is joined to point S through an inverter, the circuit will become a ___________.

a. J-K Flip Flop

b. T Flip Flop

c. D Flip Flop

d. None of the above

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

a. 6 states

b. 12 states

c. 64 states

d. 128 states

The counting sequence of a uniform counter is 000,001,011,111110,100. The counter is a ___________.

a. ripple binary counter

b. combination counter

c. ring counter

d. Johnson counter

A half adder consists of an  ___________ gate and a ___________ gate.

a. OR, NOR

b. OR, XOR

c. AND, XOR

d. NOT, XOR

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

The outputs Q and -- Q of a master-slave S-R F/F are connected to its S and R inputs respectively. Its output Q, when clock pulses are applied, will be ___________.

a. permanently 0

b. permanently 1

c. fixed 0 and 1

d. complementary with every clock pulse

The boolean expression XY+X+XY is equal to ___________.

a. 1

b. 0

c. x

d. y

Shifting the contents of a shift register one place to the left is equivalent to:

a. dividing the content by 10

b. dividing the content by 2

c. multiplying the content by 2

d. None of above

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

a. OR

b. NOR

c. AND

d. EX-OR

The most important advantage of CMOS is its ___________.

a. noise immunity

b. input impedance

c. low power consumption

d. output impedance

A multiplexer tree is needed when the number of inputs is more than ___________.

a. 12

b. 16

c. 32

d. 64

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

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

While designing a counter circuit, the preferred type of flip-flop is ___________.

a. D-type

b. R-S F/F

c. J-K F/F

d. latch

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

The most suitable gate for comparing two bits is the ___________ gate.

a. AND

b. EX-OR

c. OR

d. NAND

The addition of hexadecimal number DF₁₆ + AC₁₆

a. 11C₁₆

b. 18B₁₆

c. 15B₁₆

d. 19E₁₆

When a large number of analog-signals are to be converted to the digital form, the most suitable ADC is ___________ converter.

a. a forward-counter type

b. an up/down counter

c. a simultaneous type ADC

d. a successive approximation type

9's complement of 56 is ___________.

a. 87

b. 49

c. 43

d. 35

A flip-flop may be built with

a. NAND gates

b. AND gates

c. NOR gates

d. Any one of the above

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

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