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200V N-channel FET 200V with nsec speed?

{Henry Kiefer wrote: > > Maybe you find one atwww.ixysrf.com}

I'm curious just what about, for example, an IXZ210N50L would not work. I gather there's something on the data sheet that doesn't look good to you, but I'm seeing 500V, >>4A, rated for high dv/dt, nice low Crss at about 12pF, and 4nsec on/off times even with an ohm external in the gate circuit. Seems like close to an ideal part for your job, though it would be nice to find something with a current rating closer to what you're actually running. Some of their other parts might even be better.

Cheers, Tom

Reply to
Tom Bruhns
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"Tom Bruhns" schrieb im Newsbeitrag news: snipped-for-privacy@i42g2000cwa.googlegroups.com...

He needs a matched MOSFET die AND a good package. The parasitic inductance limits the speed considerable! If for example the gate drive omits ohmic behavior, there will be great ringing (Because the gate inside the MOSFET have a high Q). You can overcome this will strong bidirectional driving the gate. That means much voltage! TO-220 package is not good for high-speed high-current swichting. This is one of the points why RF-MOSFETs will do better. Of course, SMD is also better, just because the package is small.

BTW: I've done a (patented) high-current charge-pump back in 1996 and learned it the very hard way. The beast runs at full-cycle 300kHz push-pull with 4 MOSFETs and very-low ESR capacitors. Achieved 0.13 ohms across the whole circuit and pumped over 10 amps. That is the time you can see melding foil capacitors in just a couple of seconds. Nowadays there should be a factor of two improvement achievable.

- Henry

Reply to
Henry Kiefer

Hello Tom,

There is already some inductance ;-)

I did already suggest push-pull which would remedy a lot of problems. Hopefully the engineers there will warm up to that idea because it makes life easier.

Those are generally too low in breakdown voltage. The option is, of course, push-pull with a step-up transformer. For that scenario we'd already have the right FETs.

--
Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

Hello Robert,

Or employ a fast clamp that charges up a capacitor, then use the cap as a "kicker".

--
Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

Hello Henry, Hello Tom,

The 5v/nsec max dv/dt is a concern. Unfortunately they state dv/dt only for the two extremes. But it might be worth contacting them about more information here. I am afraid that transistors like the IXZ210N50L will blow the BOM budget though.

A large package would not be an obstacle here. A three-digit price tag might...

Reminds me of a ceramic cap that turned into bubbly green glass. The one next to it exploded and I could not find a speck of that one anymore. The supply current didn't even flinch during this episode and the amp kept on humming as if nothing had happened.

--
Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

Hello Robert,

It has poor tdoff and tf (>>10nsec), plus we'd need to parallel about ten of them which drives the capacitances to uncomfortable levels. Infineon does have some newer nice devices but I am a bit hesitant with that manufacturer after they weren't able to get samples of their BSP297 to us. Despite the fact that I told them we'd pay whatever it takes to get them across the ocean and almost two hours on the phone :-(

--
Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

"Joerg" schrieb im Newsbeitrag news:CwH6h.15655$ snipped-for-privacy@newssvr27.news.prodigy.net...

is

it

foil

I tested ceramic caps in this application but they were just to small in capacitance - ended up with 30s inparallel and the unavoidable pcb inductance problem. And to loud as a loudspeaker. Annoying clicks if the pump switched on (piezo-effect).

- Henry

Reply to
Henry Kiefer

Look at ST Micro STN1N20 or STQ1NC45R-AP.

Reply to
Robert Baer

Hello Robert,

Thanks. Whatever they mean with crossover time is a bit long but we'll order some.

This one is a bit slow but as Win hinted one has to take that data with a grain of salt. So, we'll order some of these as well.

--
Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

I've been casting about for fast MOSFETs too (though I can live with

100V but need 10W or so dissipation rating) and found that Infineon's OptiMOS series looks quite promising. But nobody seems to stock much of what is supposedly available !

Steve

Reply to
Steve Kavanagh

Hello Steve,

That's just the problem. They do not seem to understand how electronic parts are marketed. By now I believe it would take some high-level management changes over there to correct that problem. Then their sales will probably increase, big time. They need some execs who pound the pavement and regularly do spot-check visits on clients large and small. Just to feel the pulse. That's what we did in our med biz and the CEO expected it from us.

--
Regards, Joerg

http://www.analogconsultants.com
Reply to
Joerg

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