Gyrator In Series - Questions

[aziltz]

Looking at this Op Amp Gyrator example.  Can the gyrator be used as a series component by replacing the ground on the lead of R with an output terminal?

I'm thinking about how to make the standard Crybaby circuit, replacing the inductor with a gyrator.  The stock inductor does not go to ground, its actually a series connection in a feedback loop kind of thing.

[liquids]

Not a complete answer, but \here's some interesting, complimentary info....

http://www.hollis.co.uk/john/circuits.html

and scroll down for the Phantom Wah...
http://www.hollis.co.uk/john/phantomwah.jpg

[aziltz]

Thanks.  It's going to take a little work to try and recognize what's going on there.  RG has an OP version of the Dunlop Style Wah using an Inductor, so perhaps if I compare those.

[Rob Strand]

The inductor connects to a bypass cap which is ground for AC signals, in theory you should be able to use a grounded inductor.
All you have to do is get the DC bias stuff right, both of the gyrator and the things biased through the inductor.  That might
mean putting a large cap in series with the gyrator inductor.

I vaguely remember this coming up a long time ago and there were some issues using the simple gyrator.
I think I posted a schematic, the discussion should be in the archives but the schematic definitely won't.

(FYI,  there are floating inductor gyrators where the two ends are free, one paper is

A. Antoniou, Realization of gyrator using operational amplifiers and their use in RC active network synthesis, 1969.

There were a few papers following which worked out the best circuit structure for a gyrator, IIRC they are mentioned
in either Van Valenburgs's Filter book, or Sedra and Smith's Microelectronics.

The circuits are much more complicated than the grounded gyrators.)

[Rob Strand]

This might be the old thread,

http://www.diystompboxes.com/smfforum/index.php?topic=5288.0

The "issues" seem to be:
- you must use an opamp for the gyrator
- it might turn out to be a bit noisy.