[sdiy] Formant 24dB filter

[Happy Harry]

Well... the 741 does not suffer from phase reversal... but.... ;^)

H^) harry

Check out Linear Technology... some data sheets boast "No phase reversal" 
maybe their web site and a search ???


>From: Brown David <David.Brown at tms-ltd.com>
>To: "'jhaible at t-online.de'" <jhaible at t-online.de>
>CC: synth-diy at node12b53.a2000.nl
>Subject: RE: [sdiy] Formant 24dB filter
>Date: Wed, 6 Jun 2001 14:26:41 +0100
>
>This sounds plausible, although I've not come across this phase reversal
>effect before.  Can anyone suggest an opamp that DOESN'T suffer from phase
>reversal?
>
>-----Original Message-----
>From: jhaible at t-online.de [mailto:jhaible at t-online.de]
>Sent: 06 June 2001 12:22
>To: cfmd at swipnet.se
>Cc: synth-diy at node12b53.a2000.nl
>Subject: Re: [sdiy] Formant 24dB filter
>
>
>
> > Sure, it has non-inverting buffer on the output, but the input is
> > inverted. What was you hinting at? Incorrect feedback-sign or what?
> > Please speak up on the full story...
>
>Phase reversal. Once your signal is strong enough to go out of
>the allowed common mode range, negative feedback turns positive.
>As somebody else pointed out, use opamps without phase reversal,
>and the problem should be cured.
>
>DC offset has nothing to do with it. Causes a little CV
>feedthru, but won't latch the circuit up.
>
>JH.
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