Hi:

Maybe it's Magic Sine Waves promoted by Don Lancaster (http://www.tinaja.co=
m/).
Uses PWM and an H-bridge.  The key idea is to align the rising and falling =
edges precisely so that the harmonics cancel=20
each other.
Excellent cancellation can be obtained for harmonics lower than somewhere b=
etween 9 and thirty something depending on=20
the  number of bits and the precision.
http://www.tinaja.com/magsn01.shtml

At one time he sold a PIC with the Magic Sine wave firmware, but when I tri=
ed to buy one they were no longer available.
Note that he has developed both single and 3-phase versions.  For by applic=
ation (spinning up gyroscopes) the free on=20
line designs are fine.

Really want two versions.

1. 400 Hz single phase
2. 400 Hz three phase

If someone has either of these I'd like to buy it.
I'd also be willing to do an ExpressPCB board layout if a working schematic=
 is available for either or both of them.

--=20
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.

--=20
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