🚀 go-pugleaf

In article <423@bartal.CRLABS.COM> phillip@bartal.CRLABS.COM (Phillip M. Vogel) writes:
>Use something like an NE590 (Signetics 3 to 8 demux), which is
>something like a 74138 with high current high voltage open
>collector outputs.  Put all the LEDs in series with a ~20 mA
>current source driving one end (the anode), and the cathodes
>tied to each output of the 590. The only catch is that your
>current source has to be able to put out a voltage of about 15 or
>so volts, depending on the LEDs you use.

OK, this is solution #5.  I received mail from Brian Rhodefer from Tek
suggesting the same thing, but he substituted a 7445, which might be a
bit more common.

I'm curious as to the implementation of the current source, though.  What
are some favorite current source circuits?

I think National has a chip in a TO-92 case that does something like this.

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