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A project log for Random Ridiculosities and Experiments

Sometimes yah's just gots tah try somethin', regardless of whether it'll become a full-fledged "project"...

eric-hertzEric Hertz 04/21/2022 at 04:230 Comments

What to expect when you're expecting to scavenge PCBs for a diode or two:

https://www.digikey.com/short/vzrt90tv

So... if I'm lucky, it would seem Vf=0.4V at 2A is about the best-of-the-best, even in this era of switching converters everywhere, and even amongst, say, /really/ high-voltage/current diodes I might've found on old TVs, etc.

I figure old laptop mobos would probably be the best source, and sure-enough found many potential matches on a board from the early Pentium era... I'll check forward-voltages another day.

Unfortunately, 0.4V is quite a lot when power-steering between two 5V sources. And even though the diodes will save a *Couple* MOSFETs, it seems I need at least one, more likely two MORE in the chain before my device gets its power... at RDSon=0.05ohms, 2A=0.1V PER MOSFET. We're talking running a 5V device off of 4.4V, now, and that doesn't make me happy... Back to FETs, and I'll have to do another "What to expect" as I goofily thought 4 would be plenty for most my future needs many years ago, and now I need four for one friggin circuit, alone.

Yahthink RDSon=0.05ohms was common in the pentium era? What about the PBG3 era? Or maybe I'll find out that huge ol' TO-220's from old TVs will do better?

Find out in the next episode of "What to expect"

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