zapping gates

This instrument preceded MOS-FET's few years I used a Tektronix and HP ones in early '60.

Darn! I thought this was going to be another anti Microsoft rant.

-- Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com

------------------------------------------------------------------ In the force if Yoda's so strong, construct a sentence with words in the proper order then why can't he?

Prove? I just thought the numbers were interesting. The gate leakage numbers are cool, too. Who needs a reason?

Gosh.

John

This thread shows you why you can't just report a piece of information without defending it to the n'th degree. What a PITA. It was interesting to see who gave you a lot of sh*t and who took it at face value. These people do not realize that there is a gray zone between Absolute Maximum and Absolute Failure. You reported Absolute Failure which is needed info. MOSFETs may not fail if you exceed the AM. I will remember your data point the next time I smoke a MOSFET and must determine exactly what caused the failure. In catastrophic situations, many strange things happen and this may help to solve the puzzle. I remember and found it very informative, your reporting MOSFET performance to >200c. Interesting that you did not receive much grief for that report. It has be helpful to me in diagnosing some catastrophic failures. I hope that this does not deter you from reporting useful information in the future. Maybe you should distribute it as "data taken because I could". Regards, Harry

ditto. interesting.

of course it does make me wonder about the absolute failure dynamic gate voltage (c.f. DC). I think I can make a hand-wavy argument that it will be lower, and related to Tr, Tf. Alas, I do not have a 20-80V pulse generator with adjustable slope, or I'd give it a whiz.

the ESD testing would account for this, as its a charge transfer thing that happens pretty quickly. Hey, thats how to test it - charge up a cap, then smack it across the gate with a low Rdson FET. peak current very high, FET controls it and slope, and any old LV pulse gen will do. I'll give it a crack this arvo.

Cheers Terry

For a *really* fast hv edge, use a relay.

John

[snip]

Mercury-wetted. I used to make fast edge, short-width pulses by driving a shorted-termination transmission line with a mercury-wetted relay.

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

Noted, thanks guys.

with 1uF of capacitance, a 47N60S5 switching fet and an IRFBC40 DUT, with a Tektronix AFG310 signal generator, it happily ate 30 or so 60-V gate pulses. A single 90V pulse wrecked it. The edges are a bit slow,

90V in 250ns, but thats cos I've got Rg = 50.

So: if the dynamic abs-fail voltage is lower than Johns measured 80V, its not by much. I've run out of FETs I want to break (that was a left-over lying on the bench).

Cheers Terry

Un bel giorno John Larkin digitò:

The numbers are interesting indeed, and you don't have to give any reason, with "prove" I meant "prove to yourself". My english has its limitations, please be patient. :) I was meaning: why did you take the time to pick some MOSFET and zap them? Were you just curious or did you think this information will be useful for you sometimes?

Are you saying that if you will use that component for a serious design, you are going to do one or more of the above?

1) Willfully use Vgses >30V 2) Not put any protection circuit to avoid Vgses>30V, because "if I'm lucky, it's going to withstand at least 100V" 3) Choosing this MOSFET instead of another, because "in the single test I've made, it withstood a greater voltage than the other"

--
asd

Un bel giorno Paul Hovnanian P.E. digitò:

What?

--
asd

No, your English is fine.

We're having one of our products, a 17 KW peak power MRI gradient driver, blow up in the field now and then, so we were investigating failure mechanisms. It doesn't look like even severe drain dv/dt transients can couple into the gate enough to damage the fets, so that ain't it.

John