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On Thu, 24 Nov 2005 14:47:37 -0500, Phil Hobbs
wrote: John Larkin wrote: A 1N4007 can also be used as a drift step-recovery diode and as a plasma avalanche diode. Together, two can generate a kilovolt edge with a 100 ps risetime. Okay, so I'm intrigued already. I have all the hardware available--two 1N4007s and a 3 kV adjustable power supply! How do I build one? Cheers, Phil Hobbs Google "Grekhov diode." A lot of the papers are for members only, but this one gives the general idea: http://www.ece.jhu.edu/~pps/ECE777/A...ano-pulse1.pdf Grekhov discovered both the DSRD and the plasma avalanche effects in cheap power diodes. The core of the DSRD effect is that, if a PIN diode is forward biased for not too many nanoseconds, the carriers don't have time to float all around the place so the charge profile is good for a nice reverse snap. HP did the same thing in their classic 1430 12-GHz sampling head, circa 1965 roughly. This box used the DSRD effect, in a semiconductor that one would not expect to be used in an application like this... http://www.highlandtechnology.com/DSS/T220DS.html We bias the snap diode +48 volts (yes, forward direction) for about 80 ns before we turn the drive around for the snap. It was originally designed for use in a LEAP atom probe. John |
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