Folks, When looking for small-signal high voltage PNP I was disappointed. Nothing available above 500V anymore and ideally I need north of 1kV at less than 2mA. I know the old CRT TV sets are gone for good but isn't there some specialty company that still makes such high voltage transistor? In the normal range the FMMT560 at 500V and the STN9360 at 600 seem to be the end of the rope. Where the STN is officially listed for switching and I need linear but that may be ok. For NPN and FETs it doesn't look a whole lot better and they'd not be well suited in this case. There is always the option to cascade but that gets old when there are multiple strings needed. -- Regards, Joerg

1KV at 2 mA is 2 watts, not really small-signal any more. Does it gotta be PNP bipolar? Does it gotta be cheap? There are dpak n-channel mosfets up to 1500 volts. I cascode them with an optocoupler to avoid nasty gate voltage drivers. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com

No more high voltage PNP transistors?

Dec 08, 2015 22 Replies

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Tim Williams 10 years ago

Should I ever randomly come into a scientific glassblowing and vacuum kit... I've always wanted to make one.

It should be, as mentioned, painfully slow (while electron tubes have practical speeds -- transit times in the single digit nanoseconds -- ions will be *microseconds*!), and proportionally low in transconductance and perveance. Still, a few tens or hundreds of micromho (that's microsiemens for you youngsters) should be possible, at perhaps a mA or so, and 100V (plus a heater and 10-100V for the ion generator).

Keeping the drift region adequately pumped will also be a challenge. Likely, it will inevitably exhibit a hysteretic or thyratron characteristic at higher voltages/currents.

So, if you thought lateral PNP stank...

Tim

Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com

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whit3rd 10 years ago

You laugh, but storage rings find positrons more easily contained and cooled than electrons. Yes, vacuum tubes with antimatter are a real, useful, thing. Usually go by 'synchrotron'.

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Bill Sloman 10 years ago

Dirac originally envisaged positrons as "holes" in an electron sea.

It's difficult to imagine that they are anything but exactly equally as easy to contain and cool as electrons.

Colliding particles and anti-particles does have it's advantages. Equal mass and equal and opposite momentum. The fragments don't have any inherited momentum.

Bill Sloman, Sydney

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