The 45 MHz lower frequency limit is strange.
THey do have DC curves, which is refreshing in an RF part.
Rds-on, seldom specified for an RF part, looks like about 5 ohms.
I wish they had Spice models.
I do not find the DC curves in the datasheet. Can you give a hint?
"DC curves" are tables in the "View Graphs" ...
Data sheet page 3. That suggets operation down to DC.
The 45 MHz might be caused by coupling caps on the eval board or something. I want to use parts like these as switches.
Some MMICs have internal bias circuits that indeed wreck the low frequency response.
They do look interesting as switches indeed. Are they JFET-s? That gate-source +0.7V max and the max gate current suggest sort of that, although 0.7 looks too high. I have biased (during wrestling this or that, not in an end product IIRC) JFETS slightly above 0 G-S to get even less channel resistance but they must have brought that to a new level somehow.
These are phemts, which are enhancement mode parts that turn on at a few tenths of a volt. Capacitances are crazy low. We use them as switches, typically to discharge a timing ramp capacitor or some such.
I have taken a lot of data on their SAV541 and SAV551 parts, which look very similar. I can post that if anyone is interested. The SAVs have wire bonds inside; maybe these don't.
I did find remarkable effects if they are driven past suggested data sheet limits. They just keep enhancing!
The Supertex depletion-mode mosfets enhance some too.
They are not JFETS. MiniCircuits has a good summary.
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People have observed that pHEMTs seem to have relatively low flicker noise for a GHz amplifier. My guess is that this is because very clean materials and processes are needed to make a pHEMT.
Joe Gwinn
Any and all measurements welcome!
Thanks
Phil Hobbs
Package size and pinout is roughly equivalent to HP 'minipak' used for HMPP-3890/92/95.
RL
Those are the same as the SAV series, but in a different package. The $70 sample kit has both kinds.
Cheers
Phil Hobbs
The ones I've measured have 1/f corners of 10-50 MHz. With a flatband noise of 0.3 nV in 1 Hz, that gets you about 1-nV noise at 1 MHz, not awful at all.
They're great for bootstraps, as long as you bootstrap their drains as well--otherwise they make very disappointing followers.
Cheers
Phil Hobbs
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