Functional surface mount equivalent for FJN3303F?

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NGinuity
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Functional surface mount equivalent for FJN3303F?

Postby NGinuity » Sun Nov 13, 2011 2:15 am

As some of you know, I'm turning out a design for a totally surface mount model of the geiger counter and running into a little trouble finding a functional replacement for the FJN3303F (it only comes in a TO-92 Package).

So far, the closest match I can find is the STL128DN: http://www.st.com/internet/com/TECHNICA ... 173024.pdf

I know it's just a fast switching transistor for the power supply, but I was wondering, would this be fast enough compared to the 3303F? This is more of just a check step in case there aren't any gotchas I'm missing and I'm pretty sure it will do the job, but I wanted "ye olde designer" to chime in because the power supply isn't my design. :-)

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mightyohm
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Re: Functional surface mount equivalent for FJN3303F?

Postby mightyohm » Sun Nov 13, 2011 8:16 am

You could ask Duane what he is using in his SMT version:
http://blog.screamingcircuits.com/2011/ ... skimo.html

The STL128DN looks like a really good substitute for the FJN3303. I think it's definitely worth trying out. If you're going to be playing with the HVPS it is really helpful to have a scope with a 100x probe that is rated at 600V or higher.

NGinuity
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Re: Functional surface mount equivalent for FJN3303F?

Postby NGinuity » Sun Nov 13, 2011 1:52 pm

mightyohm wrote:You could ask Duane what he is using in his SMT version:
http://blog.screamingcircuits.com/2011/ ... skimo.html

The STL128DN looks like a really good substitute for the FJN3303. I think it's definitely worth trying out. If you're going to be playing with the HVPS it is really helpful to have a scope with a 100x probe that is rated at 600V or higher.


That's good advice on both accounts, I'll make a go with the STL128DN, but I'll likely be back for help if I run into issues with the power supply! I've got a 100x probe with that rating _somewhere_ in the junk, no wait, spare, no wait, work, no wait, lab room. I'm making good progress and hopefully people will like what I've done for a few of the creative solutions to problems I've encountered.

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mightyohm
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Re: Functional surface mount equivalent for FJN3303F?

Postby mightyohm » Mon Nov 14, 2011 9:41 am

Cool! Please share your design when you're finished, I'd love to see it.

NGinuity
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Re: Functional surface mount equivalent for FJN3303F?

Postby NGinuity » Tue Nov 15, 2011 11:57 am

mightyohm wrote:Cool! Please share your design when you're finished, I'd love to see it.


Of course! Wouldn't feel right if I didn't. After all, being open source, I'm sure someone would want to mess with the design at some point. I actually didn't change much of your original design. In fact, this was the first functional component I couldn't find in a surface mount package. It will get a little more interesting when I work with the connectors, but I'm striving to make even those surface mount. I literally want to be able to drop it in an altoids tin after a few holes are drilled in the sides and not have to worry about masking anything on the bottom from a short. I'm very close and hopefully will have something to send to Dorkbot when laen comes back from his end-of-November vacation.

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Re: Functional surface mount equivalent for FJN3303F?

Postby mightyohm » Tue Nov 15, 2011 12:52 pm

Sounds good. Best of luck. :D