[sdiy] OTA to voltage-control resonance?

[Magnus Danielson]

Aaron Lanterman wrote:
> 
> On Aug 30, 2009, at 7:52 PM, Jerry Gray-Eskue wrote:
> 
>> If you put it in the feed back loop I believe you will need the "Floating
>> Voltage Controlled Resistor" shown in figure 10 of the National 
>> LM13700 data
>> sheet.
> 
> Some of my students tried that - if I recall correctly it acted kinda iffy.

You must dampen the voltage difference way down or else the arctanh 
distorsion will eat you for breakfast.

>> I think the main reason the circuit is not widely used is that the more
>> common voltage control techniques work as well or better and require less
>> complexity.
> 
> Yes - you can figure out what your feedback is feeding into and design 
> some appropriate variable gain element that's simpler.

If it goes into a virtual ground, hooking an OTA directly to it sound 
like a good idea.

Cheers,
Magnus