[sdiy] integrator / capacitor leakage

[Magnus Danielson]

From: "JH." <jhaible at debitel.net>
Subject: Re: [sdiy] integrator / capacitor leakage
Date: Sat, 3 Dec 2005 13:42:27 +0100
Message-ID: <001e01c5f80b$12b3d030$0200a8c0 at jhsilent>

> Polystyrene is no problem.
> So, same configuration, same type of capacitor, what would be better?
> C/10, or level/10 + amplification?

The later. Based on my experience that expo-pairs easilly go into saturation,
the larger cap or the large amplitude, the nearer saturation you go. You loose
on the leakage limit, but you gain in tracking precission. You win some, you
loose some.

You may have solved the expo-part, you have yeat not mentioned anything about
that, but you should be aware of that as a high-freq problem.

Cheers,
Magnus

> JH.
> 
> 
> > imho the weak link is the capacitor...
> >
> > if the 'smaller' cap allows you to get into a high-quality type
> > like a polystyrene, I'd go that direction.  Its hard to get large
> > value, low leakage caps.
> >
> > Good amplifiers are easier to find.
> >
> > H^) harry
> >
> >
> >
> > jhaible at debitel.net wrote:
> >
> > > When I'm building an integrator for a triangle or sine wave oscillator
> with an
> > > amplitude of 20Vpp, I have two options:
> > >
> > > a) run the integrator at 20Vpp, or
> > > b) run the integrator at a lower voltage, and amplify the signal
> > >    with an extra amp.
> > >
> > > Now, for a certain current into the integrator, the integration
> capacitor
> > > in case (a) will be much smaller. (Larger voltage to pass in the same
> time
> > > at th esame current.)
> > >
> > > What is better, in terms of precision / leakage?
> > >
> > > At first glance, I'd say leakage is mostly leakage _currents_, so
> > > it will be the same in both cases.
> > > At second glance, I'd say if the leakage currents are not entirely
> > > independent with voltage, case (a) will be worse.
> > >
> > > Is this right? Are there other things to consider?
> > >
> > > Background: VCO which not only will run from 0.03 Hz to 20kHz,
> > > but which will also produce very precise waveforms over that
> > > whole range.
> > >
> > > Any ideas / hints welcome.
> > >
> > > JH.
> > >
> > > -------------------------------------------------
> > > debitel.net Webmail
> >
> >
>