pHEMT model tweaked for 1/f noise

I posted a slightly expanded version of this post at , with a screen shot and the .asc file link.

Cheers

Phil Hobbs

That's wonderful. I have several active uses for SAV551, both linear and switching.

The thing on the left is a 551.

I hope to finish that and fire it up tomorrow, if enough people will leave me alone.

I also have a new coaxial ceramic resonator oscillator that uses a

Your model is a bit off my DC measurements, which of course doesn't matter in most amplifier applications.

At +600 mV dc on the gate, I measured Ig = 2 uA and Rds-on = 2.2 ohms. Your model has more gate current and higher Rds-on, 230 uA and 5 ohms.

I'm driving some from 4 volt CMOS logic, high or low, through 5K resistors. Sort of like it was a bipolar transistor. The gate behaves a lot like the gate of an NPN. Like most such parts, the gate is delicate, rated 2 mA max for this one.

I might tweak your model a tad to make it a little better for switching.

Mini-Circuits does *not* have a Spice model for any of their phemts.

OK, time for my donut.

Fun. Keep us posted.

Dunno if a device with a 20-MHz 1/f corner is what you want for that, but maybe.

Cheers

Phil Hobbs

My procedure was pretty simplistic--I just stuck 30 mA through it, measured V_GS, and hacked VTO to make the two agree. I ignored base current entirely.

Cake, bread, brioche, cruller, ...?

I cordially dislike cake doughnuts, but a good maple- or chocolate-iced bread doughnut is a beautiful thing.

Cheers

Phil Hobbs

(Pecan sticky buns rule, as long as they're not the toffee ones);

Probably not. I should probably use a fast NPN.

If you have any spare time, maybe you could help with this. Some thinking, if nothing else. I think I have invented a digital PLL that I don't understand!

(Want a new DDG?)

Our nearby Safeway makes a super Boston Creme, white goo inside and cholocate icing. They make great bagels too. All their other baked stuff is terrible.

Sticky buns are wonderful, but hard to find here. We have "morning buns" that are awfully good.

The Brat is working on her Guinness Cake. She's bringing the latest revision over tonight for a design review.

Have you tried basing it on the ADS-style quadratic Curtice model for the ATF-55134?

Something like (with your noise parameters)

.MODEL SAV551 NMF(Vto=0.3, Beta=0.444, B=0.8, Alpha=13, Lambda=0.072, Rd=2.025, Rs=0.675, Cgs=0.6193E-12, Cgd=0.1435E-12, Pb=0.7, Fc=0.65, Kf=5e-11, Af=2)

although that Vto looks a bit odd; definitely needs fiddling to make it match measured parameters.

? David

Sounds like fun. Send me an email.

Very nice. More modern looking than VFDs, though not as pretty a colour.

Cheers

Phil Hobbs

That place down the hill from you, across from the used record store, had very good sticky buns.

Could make a mess of your git repos. ;)

Cheers

Phil Hobbs

I'd have to actually figure out what all those parameters do, though. ;)

Cheers

Phil Hobbs

She invented the multilayer Guinness Cake. It doesn't relly look like a draft Guinness any more, but the icing/cake ratio is advantageous.

Oh. I thought you knew.

I did read up on the noise and threshold parameters for maybe 10 minutes. I might hook one up to the HP 4145B when I'm in the lab next week--we're using a SAV-551+ bootstrap for a new photomultiplier-replacement gizmo. In certain frequency ranges it's a super good bootstrap, so it might be a good idea to try to generate a better model.

Cheers

Phil Hobbs