High Frequency High Voltage Pulse

Thread Starter

iraquois1

Joined Feb 27, 2020
16
Hi. I am trying to design a circuit to switch a 400V supply with rise time of 1 ns and 50ohm load. But at that level of voltage mosfets (which I searched) are unable to reach this speed. (As far as I know) Does anyone have an idea about how to do this?

I looked for avalanche transistors. I don't know if I can have square wave from them.

I also searched for Vacuum Tubes and don't have any experience about them so I don't know.

Any idea please? Thanks for reading.
 

Irving

Joined Jan 30, 2016
1,006
That's pretty demanding; may we know the purpose?

Also, to get that rise time your wire inductance from source to load will be critical. 20awg wire has a self inductance of around 0.4nH/mm so to achieve 1nS your maximum wire inductance will need to be << 50nH or wire length (there & back) <<125mm (excluding parasitic inductance in load and switch)
 

Thread Starter

iraquois1

Joined Feb 27, 2020
16
Thanks for your answers. I have searched for even GaN mosfets. Even they can maximum reach 2ns. There are frequency generators which is capable of creating ps rise time pulse. How do they do it ? :).
 

Irving

Joined Jan 30, 2016
1,006
There are RF power MOSFETS that will work past the HF range, like the VRF2933. That might be a good place to start.

https://www.mouser.com/datasheet/2/268/VRF2933_MP_J-1669816.pdf
But even a good RF power MOSFET won't achieve that rise time; operating in the linear region & ability to amplify a sine wave at 30MHz, or higher, says nothing about switching times; indeed, they don't even spec t(on) or t(off) for that MOSFET as its irrelevant for its purpose...
 

Papabravo

Joined Feb 24, 2006
14,393
But even a good RF power MOSFET won't achieve that rise time; operating in the linear region & ability to amplify a sine wave at 30MHz, or higher, says nothing about switching times; indeed, they don't even spec t(on) or t(off) for that MOSFET as its irrelevant for its purpose...
I never said it was a solution. What I said was that it was a place to start. What I meant by that the folks that make those parts might have other devices that might come close to meeting the TS's requirements.

What I said in my original post was:

I seriously doubt that you will easily find or be able to afford such a MOSFET.

No hint of ambiguity there.
 
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