Linear power FETs

Just 6dB gain at 40MHz - that's almost DC.

Clifford Heath.

I skipped over the s-parameters, I was more interested in the switching behavior.

It's a 500V FET with tr=3nS and tf=5nS @ Vdss=400V. That was the interesting part. Plus a decent SOA curve.

Cheers, James Arthur

Welcome back! You've been a bit scarce since last spring, iirc.

Cheers

Phil Hobbs

-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510

Nightmare, 2x2mm passivated die with solder bumps.

Sure works though. Everybody uses them in incoherent lidars--iirc the Osram triple-stack laser datasheet shows them.

Cheers

Phil Hobbs

LMG3410R070, 600V 40A GaN, 100V/ns, integrated driver and protection.

We use them. They're really no worse than any other BGA chip. EPC should offer little eval boards but for some reason don't. We made our own.

Cooling can be a problem, getting heat out those tiny pads. Topside cooling is a nuisance.

Am 11.01.19 um 02:58 schrieb snipped-for-privacy@yahoo.com:

That's probably what has become of Directed Energy. They bought die from APT IIRC and put them into their freshly developed stripline case.

They were the bee's knees some 15 years ago in ham radio amplifiers but seem to have faded away, or I did not follow it since my interest shifted to VHF+.

cheers, Gerhard

Hi Phil!

I've been doing some pretty fun things, but hobby-level electronics, nothing I thought would be very interesting for sed. I do still peek in to see what's happening.

Cheers! James

Since I'm wrestling wire-bond parasitics trying to get my FETs /moving/, passivated die with solder bumps sounds fantastic. I just wish they'd start delivering them!

Cheers, James Arthur

Cool. An internet search for "vhf fet PA power amplifier" brings up some interesting designs.

Here's one: n=77% @ 2 meters, 500W

As expected, RF guys just resonate out bond wire inductances, something I can't do when making fast pulses.

Cheers, James Arthur

Cheers, James Arthur

That's very interesting for power conversion and solid-state drives. Sweet.

I have to make accurate fast rectangular pulses with flat tops and high edge timing accuracy, so for now I'm wary of having that much complexity between my trigger and the output signal.

Thanks for the heads-up on a nice part.

(I posted the linear-mode FETs partly with you in mind--ISTR you were interested Once Upon a Time.)

Cheers, James Arthur

??? EPC eGaN FETs have been around Digikey for half a decade IIRC!

Tim

Right. That's why RF dmos fets aren't good for pulses. Some are optimized for a specific RF band.

James!, As a tadpole here on SED I'd love to hear/see any of your hobby level 'fun' stuff. The fare has been a little thin here.

I'm doing this high side switch driving a heater to ground. Looking at the circuit I got to work, I've got low pass filters everywhere, with little understanding... which happens sometimes when you're just trying to get something working.

I think my circuit was missing some resistance on the inverting input. (I tried to do some asci art, but too much of a Friday night buzz. :^)

High side GS resistor (on pfet) that is turned off by level sift 'grounded' base npn, with emitter resistor driven by opamp. A resistor divider senses drain/load voltage-compares that to error (in opamp) which drives emitter R.

George H.

That paper, while only 5 years old, is using an LDMOS FET that's more than 20 years old. The analog TV transmitters it was made for have been retired locally after decades of service. Just sayin', our Indonesian fraternity might not be up with the very latest... and they don't show their circuits either.

NXP publish a lot of good app notes and reference designs. Some of the RF power amps span well over a decade of bandwidth, limited mainly by the bandwidth of the baluns they use to transform between 50 ohms and 6 ohms (input) and 2-3 ohms output impedances. That's not really consistent with your claim that the lead inductances are just resonated out. If you look closely at the geometry of these transistors and at the reference designs themselves, in many cases the inductance starts to dominate over the capacitance only at some hundreds of MHz. So I don't think your complaint about RF FETs is entirely fair.

Google for "site:nxp.com RF power" to get all the good info.

The parasitics of a package that can produce 1800W CW over 1.8-400MHz must surely be rather small?

Clifford Heath.

You didn't read the OP, did you?

That's okay, we all put our foot in it sometimes. :-)

Cheers, James Arthur

But I called out one, above, that's spec'd to tr=3nS @ 400V. That looked promising.

Cheers, James

Excellent point. Yes, you'd think their parasitics would have to be small. "Unmatched" seems a promising magic keyword for pulse applications.

I skimmed through the listings, but I didn't notice any that switch hundreds of volts, not even the RF Cooking transistors. I need that, at the moment. (I've made some of my own R.F. 'cooking transistors,' including my first and only +23dBm 920MHz p.a.)(Of which about 2e6 were ultimately produced.)

One of my problems, currently, is that most of the high-voltage fancy FETs are monstrous compared to my needs, so even though their figures- of-merit Ron vs. Qg are worlds better than the older tech stuff, the fact that they're 20x over-sized for my application makes them slower than an appropriately-sized MOSFET.

Even the most nimble GaN garbage truck FET still isn't as gamely as a silicon itty bitty unicycle FET.

Cheers, James Arthur