In astable multivibrator using IC555 timer design, the duty cycle D is given by _______.

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RRB ALP Electronics Mechanic 23 Jan 2019 Official Paper (Shift 3)
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  1. Toff/Ton
  2. Ton/(​Ton + Toff)
  3. (Ton + Toff)/Ton
  4. Ton/Toff

Answer (Detailed Solution Below)

Option 2 : Ton/(​Ton + Toff)
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Detailed Solution

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The duty cycle for an alternating quantity describes the fraction of time that the pulse is ON in one pulse period.

Mathematically, this is defined as:

Duty Cycle = \(\frac{T_{on}}{T_{on}+T_{off}}\)

Ton = Time for which the output is ON

Toff = Time for which the output is OFF

Also, Time period is the sum of the ON time and OFF time, i.e.

T = Ton + Toff

Periodic waveform with different duty cycles is as shown below:

F2 S.B Madhu 17.02.20 D6

Note:

It does not matter if the waveform is the output from a 555 timer or from some other circuit. The duty cycle is always the ratio of the ON time and the total time period.

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