Digital Electronics - Multivibrators and 555 Timer

Exercise :: Multivibrators and 555 Timer - General Questions

26. 

What is the pulse width of the output of a 74123 if an external 4.7-k resistor and a 0.022-F capacitor are used?

A. 290 ms
B. 29 ms
C. 33.3 s
D. 290 s

Answer: Option C

Explanation:

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27. 

To obtain a 50% duty cycle in an astable 555 timer circuit:

A. tLO = tHI
B. RA = RB and short RB with a diode during the capacitor charging cycle
C. capacitor voltage must rise above 1/3 VCC
D. tLO = tHI, RA = RB, and short RB with a diode during the capacitor charging cycle

Answer: Option A

Explanation:

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28. 

What is another name for a bistable multivibrator?

A. an on-off switch
B. an oscillator
C. a flip-flop

Answer: Option C

Explanation:

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29. 

An astable 555 timer has the following number of stable states:

A. 0
B. 1
C. 2
D. 3

Answer: Option A

Explanation:

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30. 

Which mode of operation is being used when a 555 timer chip has two external resistors and an external capacitor?

A. monostable
B. pulse stretching
C. Schmitt triggering
D. astable

Answer: Option D

Explanation:

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