Re: Simple Circuit Design

ehsjr wrote:

Adding to my previous post.

It should be stated that the comparison made is
based on nominal Vf of ~ 3.2 for a white LED and
~ 1.8 for a red LED. However, at the very low
currents this circuit will produce through the
LED as the cap discharges, Vf changes dramatically.
For example, I measured a white LED Vf at 2.47 volts
with current < 100 uA. Red LEDS also exhibit a
delta Vf.

My prior reply seems to imply that there is a linear
comparison between circuit operation with a white vs
a red LED. That was not intended. I do not know
how the delta Vf compares between the red and white
LEDs, only that it exists for both, and that Vf for
the white is greater than Vf for red for all currents
from 0 to max.

Ed
.

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