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Subtract 2-4VDC at 0.1-10A+ from a DC line
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Zero999:

--- Quote from: digsys on March 04, 2020, 11:25:48 am ---
--- Quote from: Mazo --- A TL431 style reference+the amount of transistors needed to dissipate the power?All you will need to ensure is that the minimum current on the line is >quiescent current of the "TL431"
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I have thought of those, but was hoping there'd be a silicon junction that didn't vary so much. Definitely a possible fallback.

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Well there are high power LEDs of course, but they will have a similar V/I curve as any diode, just with a higher voltage. Diodes also have a negative temperature coefficient, which is bad.

I think the TL431+a power transistor is the only sane way. If you don't want a big PNP, then use a small one, with a big NPN, in a Sziklai configuration, as mentioned above. There are also lower voltage variants of the TL431, such as the TLVH431, which can go down to 1.24V.
http://www.ti.com/lit/ds/symlink/tlvh431a.pdf
digsys:

--- Quote from: Zero999 ---Well there are high power LEDs of course, but they will have a similar V/I curve as any diode, just with a higher voltage. Diodes also have a negative temperature coefficient, which is bad.
I think the TL431+a power transistor is the only sane way. If you don't want a big PNP, then use a small one, with a big NPN, in a Sziklai configuration, as mentioned above. There are also lower voltage variants of the TL431, such as the TLVH431, which can go down to 1.24V.
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Looking that way ... the diode option is just so clean and simple. No active junctions, no possible gain / feedback issues whatsoever. Mount several TO247s to a 4x4oz PCB, heat is spread out nicely. Taps ready and easy etc etc Just the stoopid Vf / current issue, and the tempco you mention. Oh well.
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