In article , snipped-for-privacy@hotmail.com mentioned...
>
> > Second, and perhaps as important, the current-mirror has serious
> > problems with Early-effect and with base-current errors. A much
> > better circuit is possible with the same or less parts count, as
> > I've shown several times here in s.e.d. in years past.
> >
> > Thanks,
> > - Win
>
> OK here is the fixed circuit using Pulse Frequency Modulation supply
> based on Hysterisys feedback.
>
>
formatting link
>
> It goes into full regulation when Vbat exceeds LED Vf by 100mV.
>
> That stupid analog current mirror circuit of mine actually has a good
> minimum voltage in the upper current source, but terrible in the lower
> mirror part. That is unavoidable is it not? I think this is because
> you can't get any gain out of a transistor with a mere 100mV bias
> accross the C-E "junction". The reason for the base current errors is
> because I needed to stay with NPN transistors because I was using a
> transistor array IC. What a pile of rubble.
Why come you didn't throw in a 100 uF bypass cap across the battery? Might help a bit.
I got on Hosfelt Electronics web site and ordered a couple c-notes worth of parts. Most of that was in the submini toggle switches, which were half the price I could find them at other places. The DPDTs were only $.65. Cheap. For some odd reason, the SPDT were more, but still cheap, $.89. I got 4 of the Mueller Kelvin Clips, and those were $7.50 each, so that added up, too. But I think I nickled and dimed too many pretty colored ultrabright LEDs. Slap my hand. But hey, it's my moolah.
But the best deal I found was the .22F 5V memory caps for only $.50 each, so I got twenty of those. I'll be on my way to completing that Forever Flasher that I ranted about earlier. Five of those only cost $2.50, which was less than the 1 farad for almost $3 at Mouser - even more at Digi-Key. :o)
(Gee, at that price, I hope they're not used! They didn't say..)
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