[sdiy] AD633 quadrature oscillator

[Roman Sowa]

That design note also says usable range of this oscillator is 100:1 so 
not much really.
The zener with a bridge is to ensure the same damping characteristics 
for positive and negative halves of the sine wave. With 2 zeners you 
might expect slight differences between them which introduces 
distortion. And also that is for temperature compensation. Zener at 
about 8V used there has positive tempco, and diodes in the bridge - 
negative, so tempcos cancel out each other.
And I think you're right, this should have thru zero FM functionality, 
as there is nothing to stop it from operation with negative control 
voltage. After all this is 2 integrators in a loop.

Roman

W dniu 2018-05-30 o 00:37, ulfur hansson pisze:
> hello list,
> 
> i'm looking to build a VC quadrature sine oscillator with the smallest 
> form factor possible - i've been eyeballing a few LM13700 based designs, 
> but rambled upon this design note from the AD633 analog multiplier 
> datasheet from Analog Devices;
> 
> 
> 
> am I right in thinking the multipliers will have through-zero FM 
> functionality? (they are 4-quadrant multipliers after all...)
> 
> also - why is there a diode bridge rather than limiting zeners on that 
> first feedback loop?
> 
> thank you!
> -ú
> 
> 
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