On 2021/04/22 2:04 a.m., piglet wrote:
On 22/04/2021 5:00 am, bitrex wrote:

There's this patent from '66 that describes a solid-state thyratron
replacement:

https://patentimages.storage.googleapis.com/42/6a/0d/6e35c415a3f0e0/US3293449.pdf


It uses a couple of SCRs. It's to replace high-power thyratrons but I
don't see why it couldn't be scaled-down.

Thanks Bitrex, that patent even mentions a tunnel diode and UJT which
are now very exotic devices. The struggle was to emulate the high
impedance thyratron grid. It seems to me (I have never seen a thyratron)
that a modern depletion mode mosfet would make a good front-end to a SCR
in that a negative grid bias is required to keep the device
non-conducting (if I understand thyratrons correctly).

Here is a conceptual sketch:

https://www.dropbox.com/s/al1b8hj07i7jfpq/SED_Thyratron_Idea.pdf?dl=0

Possible fets could be BSS126 or LND150 and SCR with sensitive gates
X0402NF or BT149G.

piglet

Yes, that might work - at least as a starting point. Need to poke at the
values a bit and keep the patent design in mind too - I suspect the
sensitive gate SCR didn't exist then.

Thanks!

John :-#)#

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