Re: Simple but precise ramp/triangle generator

From: Ken Smith (kensmith_at_green.rahul.net)
Date: 09/15/04 

Date: Wed, 15 Sep 2004 21:16:55 +0000 (UTC)

In article <4622d.7263$xH1.6650@trnddc03>,
Rich Grise <null@example.net> wrote:
>On Monday 13 September 2004 12:22 pm, Spehro Pefhany did deign to grace us
>with the following:
>
>> On Mon, 13 Sep 2004 19:01:39 GMT, the renowned Joerg
>> <notthisjoergsch@removethispacbell.net> wrote:
>>
>>>Hi Tilmann,
>>>
[...]
>> I'd use a BJT current source and a capacitor and a comparator for a
>> 50kHz sawtooth. The amplitude can be nice and stable, and I assume for
>> this application you don't care if the frequency varies a bit, so a
>> ceramic cap would work.
>>
>Just a nitpick, but does a ceramic cap actually vary, or is it just
>that with their wide tolerance, your absolute freq. could be off
>from design freq, which, of course would have some "variance" from
>unit to unit.

X7Rs are about 100 times worse than COG

COG -> 30PPM / C
X&R -> 15% from 0 C to 50C = 3000PPM 

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