[sdiy] need an op-amp that can clip without phase reversal

[Anthony Rolando]

Hey Tony, thanx for the insight. Your explanation fits the bill exactly.

Still one thing that is strange...
This circuit is a simple summing stage. So it is inverting. There is no gain, but instead there is attenuation. The circuit works nicely with the 4558. It also works fine if I reduce the input voltages, but that is not an option. Perhaps I have an error somewhere, because the TL072 def. does not work as an inverting summing amp.

Thanx again,

Tony

> Date: Thu, 14 Aug 2008 08:35:00 +0100
> From: oakleylist at btinternet.com
> To: synth-diy at dropmix.xs4all.nl
> Subject: Re: [sdiy] need an op-amp that can clip without phase reversal
>
>> I did try the the TL072 which supposedly does not latch up... well it
> did, and a whole lot.
>
> The TL072 doesn't latch up. However, if the circuit uses negative
> feedback it may appear to do so. Since the TL072 undergoes phase
> reversal when the input gets too close to the negative rail, negative
> feedback becomes positive feedback and the whole circuit slams to the rail.
>
> For example, an SVF built with the TL072 as voltage followers can show
> this effect on power up.
>
> If you use two inverting gain stages you will avoid this problem. But
> this may not an option for you. Reducing the input voltage range is
> usually the best in this case.
>
> Tony
>
> www.oakleysound.com
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy

_________________________________________________________________
Reveal your inner athlete and share it with friends on Windows Live.
http://revealyourinnerathlete.windowslive.com?locale=en-us&ocid=TXT_TAGLM_WLYIA_whichathlete_us