A word of caution...the next article in the allaboutcircuits link in Paul's posting discusses current mirrors. You *can* use that technique for multiple anodes with a few caveats
1. If you use the R1//R2 voltage divider, you will need to account for base-current of additional regulators. This means smaller R1 & R2 values, hence more power dissipation in those resistors (heat). 2. You can also use a PMOS device instead of the PNP [base--> gate, emitter --> source, collector --> drain]; the gate current will be zero. Just be careful about ESD handling procedures, and be sure to have plenty of voltage margin (Vds > 200V for Paul's circuit) 3. You can omit R2, and replace R1 with a negative voltage supply; isolated DCDC converters are perfect for this. -5V for PNP, -12V for PMOS is a god choice. Remember: the gate or base must be* negative* with respect to the emitter. Don't follow the current-mirror literally in the allaboutcircuits link, because there will be device-to-device variations in current for a given Vbe. This technique is fine for IC's when the mirrors are in close proximity on the same die and other symmetry rules are followed. Entirely different story when offchip. Having resistor R3 swamps-out the effect of Vbe variations between devices. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/2b5a6280-0266-42f8-8b8a-3cad879afed7%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
