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Jim Williams avalanche pulse generator build--modern choice for L1

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0culus:
I've decided I'm going to try my hand at this circuit as presented in App Note 47. I have some of the parts on hand (scored an armful of new in package, old stock 2N2369s at my local surplus store, for instance), but I'm putting together a BOM on digi-key to get the stuff I don't have.

For L1, he specifically calls out a Toko 262-LYF-0095K, which is discontinued by Murata it appears. There's such a dazzling array of fixed inductors available that my head is spinning trying to sort them all out. Any particular recommendations for a substitute?



Thanks!

bd139:
Two options:

1. FT37-43 ferrite core with 21 turns of wire on it.
2. Bourns radial 150uH inductors or the cheap chinese clones of them.

Pretty non critical for this one.

From the TEA thread yesterday you can see the corner of option 1 in my failed attempt to build the same circuit due to the leg falling off the LT1073 :palm:



Edit: then the bodged up non LT1073 replacement as I'm not paying £7.50 for another IC!



Also beware you might need more than 90v out of it get the transistor to avalanche so be prepared to futz with the divider a bit. This isn't one of those circuits that just works.

HighVoltage:
We had a discussion about this great pulse generator...

here:
https://www.eevblog.com/forum/blog/eevblog-306-jim-williams-pulse-generator/

and here:
https://www.eevblog.com/forum/projects/new-version-pulse-generator-(based-jim-williams-pulse-gen)/


MagicSmoker:
L1 isn't terribly critical given the tiny average current required by the pulse generator. I would look for a drum or toroidal core type with a DC saturation current of at least 200mA. E.g. - any from this pre-filtered list except for the axial types that somehow qualified as "shielded":

https://www.mouser.com/Passive-Components/Inductors-Chokes-Coils/Fixed-Inductors/_/N-wpczZ1yzvvqx?P=1z0wreaZ1z0t1rp&Rl=wpczZer9dZ1z0wrdmZ1z0wpl5SGT

However, you'll make your life a bit easier if you use a 3.6V lithium cell - or even a 9V battery - instead of a single 1.5V alkaline cell, as this will dramatically reduce the peak current needed from the cell - and which the boost inductor must tolerate without saturating; after all, stepping up 1.5V to 90V requires a corresponding 60x increase in current drawn from the source - and also allow you to use a wider range of switcher ICs than the comparatively few that will run off a single 1.5V cell.



JackJones:

--- Quote from: bd139 on September 02, 2019, 05:45:49 pm ---Also beware you might need more than 90v out of it get the transistor to avalanche so be prepared to futz with the divider a bit. This isn't one of those circuits that just works.

--- End quote ---

The switch is rated at 50V, so there isn't a huge amount of playroom. Don't futz it too far!

It uses a voltage doubler so the switch is seeing only about half of the output voltage. Going much closer to 100V might cause more problems too.

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