Phasers (AW: noise of arrays)

Joachim Verghese jocke at
Wed Jan 24 10:58:54 CET 1996

On Mon, 22 Jan 1996, Haible_Juergen#Tel2743 wrote:

> I did a spice simulation meanwhile, and I found that the CMRR is very
> dependant of the FETs' matching. So I'll better go Instrument Amp
> here, too.

I noticed that National still makes the 2N3958 dual FET (available
thru Farnell), but it isn't cheap.

> The problem with the 2024 is its reduced output swing. So I must first
> figure out a good all pass circuit with the OTA driving a virtual GND
> summing node! Any ideas?

Hmmm...can't think of anything but to use two op-amps per stage,
one as a ground referenced inverting integrator, the other as
a summer-inverter. Certainly not too elegant...or low-noise...
What about using CA3280s with pre-distortion?


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