I did the math in my head last night, but just repeated now on paper. Looks like you need to go low to high in 25us for a 20khz signal. You'd need close to a 1v per us slew. I think Check my working :)

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On 4 Jul 2012, at 07:06, "therpocc" < dmitry.shtatnov@... > wrote:

> Correct me if i wrong, but 0.4v/us is right how much wee need to process 10vpp ideal 20 kHz triangle waveform. One half-cycle is equal to 10v slew in 25us. Simple calculations give us exactly 0.4v/us to achieve this slew rate. Maybe this parameter is often overrated or requires some special conditions like +-18v power or some specific input impedance range
>
> btw, if slew rate is so important parameter, we can try to replace OA in an oscillator and possible increase frequency range. I'll try to mess up with it later.
>
> --- In Doepfer_a100@yahoogroups.com , Jim Credland <jim@...> wrote:
> >
> >
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> > On 3 Jul 2012, at 21:11, Jim Credland <jim@...> wrote:
> >
> > > I chucked the lm324s out of a previous design here, the dirty cheap and pin compatible tl084 sounds lots better. I think the slew rate was killing me. Alright for fast signals as long as the voltages were low, but with a 7v peak to peak signal it's gotta be rolling off at the top
> > >
> >
> > Just to finish my own email. I think the 324 is about 0.5v/us, which if my mental math is right must mean it starts to do bad things at about 5khz. I didn't measure the noise - i imagine there are better chips than the 84 for that.
> > J
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