How to calculate the duty cycle of this circuit

[WinterInJuly]

calculate duty cycle

Hi all!
Does anyone know how to calculate the duty cycle of this circuit? the frequency =1/RC
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[IanP]

how to calculate duty cycle

It needs the same time to charge capacitor 0.22µF through 22MΩ and dischage it through the same way, so the duty cycle is 50%.
Regards,
IanP

 

[Btrend]

calculating duty cycle

u can run a simulation to get the answer!
anyway, from hand calculation, the duty cycle should be 50%.
and the negative input should charge and discharge with the same rate between 0.12Vdd to 0.88Vdd.

 

[WinterInJuly]

how to calulate duty cycle

Thanks
How to modify this circuit to change the duty cycle? For example, i want the duty cycle is only 5%
Regards

 

[IanP]

how do you calculate the duty cycle

Use an ordinary diode such as 1N4148 and 1MΩ variable resistor.
Connect the diode in series with VR and connect this circuit in parallel to resistor R.
By changing direction of a diode you will be able to adjust high or low ratio
If you use two diodes and VR between them connected in such a way that the middle pin of VR will be connected at one side of R and both diodes at the other end of R you will be able to adjust duty cycle from, say, 5% to 95%.
Regards,
IanP

 

[WinterInJuly]

how to calculate duty cycle %

I know this circuit.
Thanks again
Regards