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# Digital Electronics - Multivibrators and 555 Timer

### Exercise

"I never see what has been done; I only see what remains to be done."
- Marie Curie
16.

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

 A. Rint = 2 k, Cext = 0.012 nF B. Rint = 2 k, Cext = 0.012 F C. Rint = 4 k, Cext = 0.012 nF D. Rint = 4 k, Cext = 0.012 F

17.

What controls the output pulse width of a one shot?

 A. the clock frequency B. the width of the clock pulse C. an RL time constant D. an RC time constant

18.

Does the 74123 one shot have an internal timing resistor?

 A. yes B. no

19.

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 ________.

 A. value of the RC timing components B. amplitude of the input trigger C. frequency of the input trigger D. magnitude of the dc supply voltage

20.

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

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