Possible Low Noise Candidates - Power BJTs

Are there PNP complements?

Hmm, not to those exactly, it seems. But there are others that do:

Tim

KSC1173, KSA473

Some at Mouser.

Stupid collector current can make for super low voltage noise, but you'll get a heap of base current, with its side effects, like shot noise.

AoE3 has a table of low-noise transistors, page 501. The best one gets down to 0.18 nV/rthz at 25 mA.

The worst non-Darlington is my favorite gumdrop, BCX70, at 3.5.

And 60 pF for a 10A transistor? That's gonna make a fast turn-on switch (turn off will be slower, saturation). I've always wanted to experiment with making plated-through holes by inserting a wire and making it explode...

I've always wanted to experiment with making

I did a bunch of experiments with exploding wires. Almost all the tests we re with .002 inch dia. wire about .25 inch long and exploded by dumping a 1 ufd cap charged to about 2000 volts.

It makes a nice pop, but there is not enough material in a .002 inch dia, w ire to make a plated thru hole.

I would calculate how much material you need to deposit a 2 or 3 mil layer on your hole. And then figure out how big a diameter wire has to be to put that much material on the hole. That should give you a ball park figure f or the wire diameter. Then figure how much energy is needed to vaporize th at size wire. You should be able to find the fusing current for that size wire somewhere on the internet. And since you want to vaporize the wire yo u probably need at least three times that much current.

I think if you do those calculations you will decide it is not worth trying .

Dan

Well, direct deposit to finished size would be unlikely to work, for these reasons, and probably thermal reasons too (how much molten copper can you spatter against the surface of FR-4?).

That said, a flame-spray method might not be too bad. Not sure how well FR-4 takes to that sort of thing. (It's not as preposterous as it sounds: lithium polymer cells are joined with zinc flame spray. It may help that they use a high temperature insulator like polyimide, or a thermoplastic that melts rather than breaks down.)

But more reasonable would be using a thin layer to render the surface conductive, and electroplating that up.

One can reproduce all the steps industry goes through to create a finished panel -- including tin plate resist if you like, but just depositing conductive ink, or electroless copper (or exploded or flame-sprayed copper!), then plating that up to finished size, isn't far-fetched by any means. :)

Tim