[sdiy] quadrature sine wave oscillator question

[jhaible at debitel.net]

There's a schematic for this in Tietze/Schenk 
Halbleiterschaltungstechnik. But it shows
generic multipliers. It's an interesting circuit,
but you probably need very good multipliers
(offset voltage!) to get the required operation,
so I never tried it, and used a triangle VCO
+ waveshaper instead.

JH.


> has anybody dealt whith those?
> 
> This looks like a state var filter, but the Q
> regulation is set up so that a sine wave can build
> up.
> 
> To prevent heavy saturation and distortion a amplitude
> regulation is needed, like in all low distortion designs
> be it Wien bridge or else.
> 
> Unfortunately the gain/phase characteristics change
> a lot if the frequency is changed a lot, so
> the regulator must work fast.
> 
> Usually this is done via saturation devices (zeners etc.).
> This will cause some distortion.
> Or by some peak detector and very slow lowpass filter.
> 
> If the quadrature outputs are squared und summed up,
> this term will be DC (ideal) and can be taken for
> instanteneous amplitude regulation:
> 
> SQR(sin(x)) + SQR(cos(x)) = 1
> 
> I know there was a single chip or hybride package for
> this. Has anybody tried to build an audio range quadrature
> VCO using this method?
> 
> Cheers
> Martin Czech
> 
> CAD/CAE Library Group
> Micronas GmbH
> Hans-Bunte-Str 19
> D 79108 Freiburg
> Tel.: +49-761-517-2422
> FAX.: +49-761-517-2258
> http://www.micronas.com
>  
> 
> 
> 




-------------------------------------------------
debitel.net Webmail