Latches, Flip-Flops, and Timers MCQs

1. An active HIGH input S-R latch is formed by the cross-coupling of

(a) two NOR gates

(b) two NAND gates

(c) two OR gates

(d) two AND gates

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Answer. a

3. For what combinations of the inputs D and EN will a D latch reset?

(a) D = LOW, EN = LOW
(b) D = LOW, EN = HIGH
(c) D = HIGH, EN = LOW
(d) D = HIGH, EN = HIGH

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Answer. b

4. A flip-flop changes its state during the

(a) complete operational cycle
(b) falling edge of the clock pulse
(c) rising edge of the clock pulse
(d) both answers (b) and (c)

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Answer. d

5. The purpose of the clock input to a flip-flop is to

(a) clear the device
(b) set the device
(c) always cause the output to change states
(d) cause the output to assume a state dependent on the controlling (J-K or D) inputs.

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Answer. d

6. For an edge-triggered D flip-flop,

(a) a change in the state of the flip-flop can occur only at a clock pulse edge
(b) the state that the flip-flop goes to depends on the D input
(c) the output follows the input at each clock pulse
(d) all of these answers

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Answer. d

7. A feature that distinguishes the J-K flip-flop from the D flip-flop is the

(a) toggle condition

(b) preset input

(c) type of clock

(d) clear input

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Answer. a

8. A flip-flop is SET when

(a) J = 0, K = 0

(b) J = 0, K = 1

(c) J = 1, K = 0

(d) J = 1, K = 1

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Answer. c

9. A J-K flip-flop with J = 1 and K = 1 has a 10 kHz clock input. The Q output is

(a) constantly HIGH

(b) constantly LOW

(c) a 10 kHz square wave

(d) a 5 kHz square wave

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Answer. d

10. A one-shot is a type of

(a) monostable multivibrator

(b) astable multivibrator

(c) timer

(d) answers (a) and (c)

(e) answers (b) and (c)

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Answer. d

11. The output pulse width of a nonretriggerable one-shot depends on

(a) the trigger intervals

(b) the supply voltage

(c) a resistor and capacitor

(d) the threshold voltage

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Answer. c

12. An astable multivibrator

(a) requires a periodic trigger input

(b) has no stable state

(c) is an oscillator

(d) produces a periodic pulse output

(e) answers (a), (b), (c), and (d)

(f) answers (b), (c), and (d) only

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Answer. f