SV: Re: [sdiy] Hopf bifurcation VCOs....... my test results!

[karl dalen]

--- Ian Fritz <ijfritz at earthlink.net> skrev:

> At 04:48 PM 11/11/05, karl dalen wrote:
> >This is a really a cool cirquit!
> >You deserves DIY nobel price for publishing it Ian!
> >Why havent you done it earlier? :)
 
> LOL!  AD did it years ago!

Boohoo, its nots your cirquit, you are a pretender! :)
(Still its a darn neat cirquit!)

> >Heres my tests reults:
> >LM13700, batch 9642, LF353 intg, TL072 feedback.
> >
> >I changed the cirguit gain a bit, 10K ,390 ohm OTA inputstage,
> >and 5,1 v zeners (i didnt have any other at the moment)
> >220k to + input at + feedback stage, otherwise all the same.
> 
> Should work about the same. Different levels maybe.

Different levels there be.
 
> >I also use one expo tied to both Iabc inputs, no reason to use separate
> expos.
> 
> Same here.  Iabc's connected through 22k to a common bias source.
> 
> 
> >Sinus has no dent!!!!!!!!!!!!!
> 
> Nothing to make a dent. All smooth functions.

Yes i know but im ""used"" to have dents in my sines you see! :)
 
> >I wanted to get rid of the trimmers so i just did the 10K, 390ohm
> >input, still perfect symetry!!!! And that "with or without" diode
> >biasing, it simply dosent matter!!
> 
> Well, sounds like you were lucky to have good OTAs.  It always seems a bit 
> of a crap shoot.

Tried a NE5517 batch 9917 same symetry but longer start time!
Ugh! What's this!!!
 
> >Mine "decreases" slightely in amplitude?!(LF353 as opamps).
> >Have to investigate that futher!
> 
> Well this gets into some fine second order effects.

Yupp!
 
> >With your schemo and my gain scaling i get instant start up at any
> frequency!
> 
> Hmmm... That seems odd, since my results and Harry's simulation both show 
> hundreds of cycles to build up.  The smaller feedback R should help some, 
> but I'm surprised at this result.

Sorry im using 4,7n instead of 47n, but that shouldent differ tought,
hmmm ,but im using higher gain in feedback stage! i'll be back!
Peculiar, what have i "done right" this time!

 
> >It sweeps all right manually.
> 
> Ah, good.
 
> >I made it to over saturate badly into crude and unbalanced
> >square waves, still performs as nice as prevoiusly, this is a
> >very stable cirquit!
> 
> Yes, stable it is. :-)

You'r starting to sound like yoda!

And im the novice! :)

KD