Multivibrators and 555 Timer MCQs

Question 1

A crystal demonstrates the ________ effect when a mechanical force across the crystal causes a small voltage to be generated.

Accepted Answer

piezoelectric

Answer

photoelectric

Answer

Co-pitts

Answer

flywheel

Question 2

What is the difference between an astable multivibrator and a monostable multivibrator?

Accepted Answer

The astable is free running.

Answer

The astable needs to be clocked.

Answer

The monostable is free running.

Answer

none of the above

Question 3

The output of the astable circuit ________.

Accepted Answer

constantly switches between two states

Answer

is LOW until a trigger is received

Answer

is HIGH until a trigger is received

Answer

floats until triggered

Question 4

Design a circuit using a 74121 to convert a 33-kHz, 30% duty cycle waveform to a 33-kHz, 60% duty cycle waveform.

Accepted Answer

Rint = 2 k, Cext = 0.012 F

Answer

Rint = 2 k, Cext = 0.012 nF

Answer

Rint = 4 k, Cext = 0.012 nF

Answer

Rint = 4 k, Cext = 0.012 F

Question 5

What controls the output pulse width of a one shot?

Accepted Answer

an RC time constant

Answer

the clock frequency

Answer

the width of the clock pulse

Answer

an RL time constant

Question 6

In a typical IC monostable multivibrator circuit, at the falling edge of the trigger input, the output switches HIGH for a period of time determined by the ________.

Accepted Answer

value of the RC timing components

Answer

amplitude of the input trigger

Answer

frequency of the input trigger

Answer

magnitude of the dc supply voltage

Question 7

A monostable 555 timer has the following number of stable states:

Accepted Answer

1

Answer

0

Answer

2

Answer

3

Question 8

What is the difference between a retriggerable one shot and a nonretriggerable one shot?

Accepted Answer

The output pulse can be stretched with a retriggerable.

Answer

The nonretriggerable can only be triggered once.

Answer

The retriggerable can be triggered many times.

Answer

The output pulse can be stretched with a nonretriggerable.

Question 9

Triggering a retriggerable one shot during pulse generation will:

Accepted Answer

extend the pulse to this trigger width

Answer

time out the original pulse

Answer

have no effect

Answer

double the original pulse width