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High-voltage, high-speed pulse generator

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mbless:
I have a project requiring the pulse-echo ultrasound technique, so I've been looking around for fast, high-voltage pulse generators. I came across this paper "A Low-Cost, High-Performance Pulse Generator for Ultrasound Imaging" that looks perfect for my use, so I want to start out by reproducing the circuit and then work on a more modern version. I assume I'm not allowed to attach the paper here, but I'll post the relevant images.

I want to achieve pulses widths ranging from 20-500ns with voltages of -200 to -500V. The figures in the paper shows it can achieve a pulse width of 10ns with -110V peak (bottom left graph), or 40ns width with -350V (top right graph). It reaches -350V in ~20ns. These numbers look great to me, so that's why I want to start with replicating this design. The schematic is also quite simple.

The schematic has 3 parts: a high impedance input, a triple push-pull gate driver, and the output stage. The paper is from 2002, so only 2 of the 4 active components are still made, which gets to why I am posting.

I can't buy the Supertex (now Microchip) VP1304. There is the VP2106, which would complement the VN2106, but you can see the input capacitance increased from 20pF to 45pF which rise & fall times increasing by 2-3ns. I imagine this is close enough but wanted to get your thoughts since the original circuit was reaching -350V in 20ns.

The other part I can't buy is the 501N04 mosfet that was made by Directed Energy, who was bought by IXYS, who was then bought by Littlefuse. Well, Littlefuse has discontinued the IXYS RF line, so I have no chance of buying that mosfet. The closest one I can find is IXYS IXZH10N50L2A. Its typical gate threshold is 2V higher (5.4V vs. 3.4V) than the 501N04, and the input capacitance increases from 570pF to 611pF. Again, I'm worried the slightly worse specs will slow down the output slew rate. Also, it's a THT and not SMD, so I imagine the increased lead inductance won't help.

Thank you for any feedback! I also welcome suggestions of more modern designs that use different drive architecture or different mosfets like GaN FETs, etc.

KE5FX:
I'd suggest taking a look around page 246 in the Art of Electronics x-Chapters volume.  It should give you some good pointers.  That particular page describes a 500V 20A 20 ns pulser made with currently-available parts.

The one in your paper will be more robust simply because the gate drivers won't tend to explode like Hill & Horowitz's initial attempt did.  They recommend TC4422 drivers for use at repetition rates near 10 MHz.

mbless:

--- Quote from: KE5FX on June 07, 2020, 06:08:27 am ---I'd suggest taking a look around page 246 in the Art of Electronics x-Chapters volume.  It should give you some good pointers.  That particular page describes a 500V 20A 20 ns pulser made with currently-available parts.

The one in your paper will be more robust simply because the gate drivers won't tend to explode like Hill & Horowitz's initial attempt did.  They recommend TC4422 drivers for use at repetition rates near 10 MHz.

--- End quote ---

I didn't know there was an x-chapters book, so I'll look into that.

Thanks for the reminder about repetition rate. Mine need is <10kHz.

tggzzz:
These have been discussed on comp.arch EDIT: I meant sci.electronics.design (doh!); you might be able to pick up some hints there, but no complete circuits.

Look for posts by Win Hill and John Larkin.

mbless:

--- Quote from: KE5FX on June 07, 2020, 06:08:27 am ---I'd suggest taking a look around page 246 in the Art of Electronics x-Chapters volume.  It should give you some good pointers.  That particular page describes a 500V 20A 20 ns pulser made with currently-available parts.

--- End quote ---

It turns out that section is a sample they've posted on their website! Section 3x.15.3 is an negative high-voltage pulser, so I have an alternative to the one in my original post.


--- Quote from: tggzzz on June 07, 2020, 01:26:23 pm ---These have been discussed on comp.arch; you might be able to pick up some hints there, but no complete circuits.

--- End quote ---

I didn't know about that group. It's hard to search but I've found some interesting topics.

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