Electronics: Unsolved Multiple Choice Questions on Basic Digital Electronics

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Electronics: unsolved Multiple Choice Questions on Basis Digital Electronics
MCQ QUIZ Sample test on
Flip Flops
Basics of Digital Gates
Hardware Families like IIL TTl CMOS
Combinational Circuits
Sequential Circuits
Propagation Delay

1. A 1 msec pulse can be converted into a 10 msec pulse by using
(a) an stable multivibrator
(1) a monostable multivibrator
(c) a bistable multivibrator
(d) flip-flop

2. The fastest mode of data transfer from CPU to memory in a microprocessor is
(a) memory mapped I/O
(b) I/O mapped I/O
(c) Interrupt driven I/O
(d) DMA

3. Flat top sampling of baseband signals leads to
(a) aliasing
(b) aperture effect
(c) under-sampling
(d) impossible reconstruction.

4. How many steps are there in the output of10-bit D/A converter?
(a) 1023
(b) 1024
(c) 10
(d) 100

5. Which one of the following can be used to change data from spatial code to temporal code?
(a) Shift registers
(b) Counters
(c) A/D converters
(d) Combinational Circuits

6.For a six bit ladder D/A converter which has digital input of 101001, the analog value is
(assume 0 = 0 Vand 1 = + 10 V)
(a) 0.423
(b) 0.522
(c) 0.641
(d) 0.923

7.Which one of the following is a D to A conversion technique?
(a) Successive approximation
(b) Weighted resistor technique
(c) Dual slope technique
(d) Single slope technique

8.If the memory chip size is 256 x l bits, then the number of chips required to
make up 1K (1024) bytes of memory is

9.Which of the following statements are correct?
1. A flip-flop is used to store 1-bit of information
2. Race-around condition occurs in a J-K flip-flop when both the inputs are 1.
3. Master-slave configuration is used in flip-flops to store 2-bits of information.
4. A transparent latch consists of a D-type flip-flop.

10, The greatest negative number which can be store in a computer that has 8-bit word length and uses 2’s complement arithmetic is
(a) -256
(c) – 128
(d) – 127

11. A retriggerable monoshot is one which
(a) can be triggered only once
(b) has two quasi-stable states
(c) cannot be triggered until full pulse has been outputted.
(d) is capable of being triggered while the output is being generated.

12. A carry look ahead adder is frequently used for addition because, it
(a) is faster
(b) is more accurate
(c) uses fewer gates
(d) costs less

13. When signed numbers are used in binary arithmetic, then which one of the following notations would have unique representation for zero? -
(a) Sign-magnitude
(b) l’s complement
(c) 2’s complement
(d) 9’s complement

14. The number of switching function of 3variables is
(c) 128
(d) 256

15. The gate whose output is LOW if and only if all the inputs are HIGH, is
(c) OR
(d) AND

16. In computer terminology 1 M Byte memory means
(a) 1000000 bytes
(b) 1000024 bytes
(c) 1024000 bytes
(d) 1048576 bytes

17. A unit pulse input is given to a single-pole stable digital filter. Its output response will be?
(a) constant pulses
(b) exponentially decaying pulses
(c) impulse
(d) exponentially rising pulses

18. The number of flip flops required in a decade counter is
(a) 2
(b) 3
(c) 4
(d) 10

19. A square wave with a period of 10 micro sec drive a flip flop. The period of.the output signal.will be
(a)100 micro sec
(b)20 micro sec
(c) 10 micro sec
(d) 5 micro sec

20.A digital Voltmeter has 4 and 1/3 digits display .The 1 volt range can read upto
(b) 1.1111
(d) 19999

21. Ultraviolet radiations are used in IC fabrication process for? -
(a) diffusion
(b) masking
(c) isolation
(d) metallization

22. In PCM system if the quantization levels are increased from 2 to 8, the relative bandwidth requirement will
(a) remain same
(b) be doubled
(c) be tripled
(d )be four times

23. The 7-bit Hamming code (even parity check) 001 for a BCD digit is known to have a single error. Therefore, encoded BCD digit is
(a) 9
(b) 5
(c) 3
(d) 0

24. If NxN = (7601 ) where N is a positive integer, then the value of N is
(a)(241)base 5
(b)(143) base 6
(c)(165)base 7
(d)(39)base 16

25. The input-output equation of a system is given by
y(n)=x(n) square
where y(n) and x(n) represent output , input sequences respectively. The system is
(a) linear and causal
(b) linear and noncausal
(c) nonlinear and causal
(d) nonlinear and noncausal.

26. The number of comparators required to build a 5-bit Analog to Digital Converter (ADC)is
(a) 5
(b) 11

27. A 555 timer can be used as
(a) an astable multivibrator only
(b) a monostable multivibrator only
(c) a frequency divider only
(d) an astable multivibrator or a monostable muttivibrator or a frequency divider

28. A synchronous sequential circuit is to be designed which will produce an output ‘1’ when previous two and present input represent an even number, with present input being least significant bit. The minimum number of states of the machine will be
(c) 4

29. The specification for a standard 74 series TFL gate reads propagation delay as 35 ns and power dissipation as I mW. This circuit is
(a) high speed TTL
(b) low power TTL
(c) standard Schottky TTL
(D) low power Schottky TTL

Directions : The following question consists of two statements, one labelled as the ‘Assertion (A) ‘and the other as ‘Reason (R) “. You are to examine these two statements carefully and select the answer’ to this question using the code given below.
Assertion (A) The modernization process has challenged the hold caste system in India.
Reason (R) Mobility as a phenomenon of change in caste system does not challenge the basic structure of caste.
(a) Both A and R are individually true and R is the correct explanation of A
(b) Both A and R are individually true, but R is not the correct explanation of A
(c) A is true, but R is. false
(d) A is false, but R is true

Assertion (A):A programmable Read only-Memory can be used as a synchronous counter
Reason (R) : Each memory location of a programmable Read- Only-Memory is programmable and can be read synchronously.

30. Assertion (A): Master slave f flip flop is commonly employed in high speed synchronous circuitry.
Reason (R) It uses two JK flip flops in cascade.

31. Assertion (A) : A demultiplexer cannot be used as a decoder.
Reason (R): A demultiplexer selects one of many outputs whereas a decoder selects an output corresponding to the coded input.

32. Assertion (A) : In analog computation only summing amplifiers and integrators
Reason (R) : The differentiators using operational amplifiers cannot be designed.

33.Assertion (A) : Self-biasing is generally used for a CE amplifier
Reason (R) : The design of self-biasing circuit is very easy as compared to other

34. Assertion (A) : 2’s complement arithmetic is preferred in digital computers
Reason (R) : To obtain the 2’s complement of a number, the hardware required is simple.

35. Assertion (A): XOR gate is not a universal gate.
Reason (R) : It is not possible to realize any Boolean function using XOR gates only.

36.Assertion (A) : ECL gate has the highest speed of operation
Reason (R) : The transistors in ECL gate operate in the active region.

37. Assertion (A) : The basic operation of a micro-processor consists of fetching and execution of instructions one by one
Reason (R) The instruction set of a microprocessor is stored inside the ALU

38. Assertion (A) In a heterodyne digital counter, the input signal is heterodyned to a lower frequency
Reason (R) The gating and counting circuits of a digital counter cannot handle GHz signals.

39. Assertion (A) Dual-slope A/D converter is the most preferred A/D conversion approach in digital multimeters.
Reason (R) Dual-slope A/D converter,provides high accuracy in A/D conversion while at the same time
suppressing the hum effect on the input signal.

40. Assertion (A) A digital multiplexer can also be used to implement combinational logic function
Reason (R) In a combinational circuit, the current output depends on the previous outputs also.

41. Assertion (A) The sampled data system with its characteristic equation
Z2- 4z + 4 = 0 is unstable
Reason (R) : Sampled data systems with positive roots of the characteristic equation are unstable.

42. Assertion (A) Fast events can be captured and displayed by a real-time spectrum analyzer.
Reason (R) All components of a signal are presented simultaneously in the frequency domain. In swept type spectrum analyzer, frequencies are supplied one at a time at a particular rate.

43. Assertion (A) Among RAM and ROM, ROM is used as firmware memory
Reason (R) ROM can be accessed for alteration.

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