[sdiy] adding PWM to a cmos clock?

[Scott Nordlund]

If you understand how PWM works, you'll understand why that approach won't get anywhere.  You can't put a square wave into a comparator and expect to get PWM out.  However, you can take the signal from the 40106's input (the voltage across the capacitor).  The capacitor is charging and discharging exponentially, so you'll be able to get PWM out of this, though the waveform is a little different from a triangle wave.  Also this signal will have a smaller amplitude than the output, so you may want to amplify it first.

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> From: subjectivity at hotmail.com
> To: synth-diy at dropmix.xs4all.nl
> Date: Sun, 17 May 2009 12:58:17 +0000
> Subject: [sdiy] adding PWM to a cmos clock?
>
>
> right now i am using a high freq 40106 clock run from +5 and 0 volts. the cap value is around A 560PF.
>
> i would love to add pwm to this circuit.
>
> i tried simply running the out of this circuit into the NON INVERTING in of a 324 running off of +5 and ground, with a buffered pot going from grnd to 5volts and plugged into the non inverting input.
>
> the results were terrible.
>
> if anybody could point me in the right direction i would appreciate it as i KNOW PWM sounds good in the circuit i am working on but the 555 clock i got sucssful pwm with has far too small a range.
>
> thanks so much
>
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