Anyone have a favorite Dual Darlington (NPN)? I was just told today that the part we were using (Zetec ZDT605) has been discontinued. I'm just about ready to finish a board, but need a current mirror and was planning to steal one off another (similar) design. Since we can no longer get the Zetec part I now have two boards to redo.
Other ideas?
DigiKey still has about 479 of them, maybe you can buy some breathing room. What current does your current mirror run at?
I wonder if these can work well in a mirror? It's a painful matter of requiring good Q1a-b beta match to achieve Q2a-b Vbe match. If there was an extra pin available, one could add a Vbe resistor and fix the problem, but....
That may be enough to prevent a re-spin of the current board but=20 won't be nearly enough for the new product. I didn't see any supply=20 there earlier today. I'll certainly snarf them up tomorrow. =20 Thanks!
The current design requires 100mA or so, to share (DC) power from=20 two (AC) balanced lines. The new application is simply a voltage=20 monitor needed to detect when the line/termination drops out. I=20 need to share the load of an opto-isolator between the two balanced=20 lines, so a couple of mA.
It works well enough in the power sharing application now. I'd like=20 to do better (eliminate the whole thing), but time and risk is=20 getting to be an issue. It's easy to justify "works".
--=20 Keith
FWIW, Quest also claims to have 3800 pcs. of the ZDT605TA for 30 cents apiece.
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