SV: Re: [sdiy] ca3080-based tri-to-sine

[Karl Ekdahl]

well, if i did understand all the math-talk in the
paper i'd find the error, but it's way over my league
right now...  what i gather from looking at the
schematic is that the ca3080 forms a comparator where 
i get

Vin+ = +-0.01498V (Iin+ = +-68uA)
Vin- = +-0.078V

and the outcome is
(Vin+ - Vin-) * gm = Iout

where gm is the magic OTA transcoductance variable
that i can't figure out how it works, only that it's
getting 15/220000=0.68uA in.

i can't see how this is going to shape anything into a
sinewave though, trying to input it into a graphic
calculator (www.graphcalc.com) yields nothing like a
sinewave...

i've obviously got something seriously wrong here...

Karl

--- Paul Perry <pfperry at melbpc.org.au> skrev:

> The theory here, is that the output top and bottom
> squashes into a sine when the OTA is over driven.
> 
> How much inpuut it takes to do this, depends on
> the gain of the OTA which is in turn set by the 
> current to the gain pin (NEVER exceed 2ma)
> and (possibly) by the power supply voltages.
> 
> best, paul perry Melbourne Australia
> 
> ----- Original Message ----- 
> From: "Karl Ekdahl" <elektrodwarf at yahoo.se>
> To: <synth-diy at dropmix.xs4all.nl>
> Sent: Thursday, October 13, 2005 8:51 AM
> Subject: [sdiy] ca3080-based tri-to-sine
> 
> 
> Hi list, i am trying to make a ca3080 tri-to-sine
> from
> a paper by Bernie Hutchins work... I have the right
> input voltage, though i'm a little bit confused as
> to
> if there's any current-requirements...  anyhow, if
> there's anything common to look for in this (really)
> simple schematic please give me a pointer...
> 
> thanks
> 
> Karl
>