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Re: gEDA-user: A couple o' questions
On Saturday 08 April 2006 04:40 pm, John Doty wrote:
> > However, your other example of the op amp with the output grounded has
> > knocked me down. Very smart application!.
>
> Ran into that one about 30 years ago when I was a grad student at
> MIT. Mike Shao, another grad student (now Mr. Optical Interferometry
> at JPL) had gotten a piezoelectric actuator driver from somebody but
> couldn't figure out the strange topology, asked me to explain it to
> him. Cascode transistors on the low voltage rails carried the current
> out from the opamp to high voltage rails, where there were mirrors,
> making a transconductance amplifier that had an output swing of
> several hundred volts, just the thing to drive a piezo. I don't know
> who came up with this.
While I'm sure Linear Tech. did not come up with, it is explained
here for anyone interested:
"How to Ring a Phone with a Quad Op Amp"
Summary:
http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1042,C1031,C1061,P1266,D4338
Detailed description:
http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1154,C1009,C1045,P1657,D4174