Light dimming comparator problem

I would like some help on a circuit I came across on the
internet. I am trying to generate PWM by going thru a
comparator. +input is fed 0 - 10vdc and -input gets fed
a ramp which is in sync. w/ the ac line freq. The lights
dim up and down OK, however I notice jitter on the ramp when
the 0 - 10vdc signal is changed. This is a problem because
I would like to feed this ramp signal to more than one light
channel. I tried an op amp(LM324) wired as a comparator
and a comparator(LM339).
Both give about the same results. Any ideas as to how to get
rid of this jitter?
Thanks.
I tried a buffer as someone suggested, but that didnt help. I used a lm324 as
a unity gain amp between the ramp circuit and the comparator.

Can you post the circuit? Are you using lamps or LEDs? Andy

Thanks for responding. I will try to post this circuit , but I dont currently have
a circuit that is postable. It will drive 120vac Xmas lights(16 channels).
The problem I mentioned is present whether lights are connected or not.
I suspect it has something to do with the way Op amps respond in general
with how I am wiring the Op amp. The - input gets a 120hz ramp signal and
the + input gets a changing DC voltage between 0 and 5 vdc(depending
upon how bright you want that string of lights). This configuration just
makes the Ramp that feeds the - input to jitter. I do have a 400 ohm
pull up to + resistor on the out put. It helps but not enough.

I'm only guessing that you get your ramp from a capacitor connected to an op amp oscillator. If so you may need to buffer the ramp with another op amp to lower the impedance.

Response

Yes, the oscillator is a LM358 wired as an integrator with a capacitor between the input and output. I will try a buffer amp as you suggested and see what it does.
Thanks.