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READER FEEDBACK
Continued from page 8
on my articles. Using LEDs for audio
communications sounds like a neat thing to
do. I would be curious to see the circuit Mr.
Bennett used to do this, as I think this would
be a great project for my students to
attempt. I did experience some problems
with the blue LEDs that I need to investigate
later, so infrared, red, orange, yellow, and
green should work as the LED photometers
I wrote about in the column. Sometimes it
amazes me with what we can do with a
handful of parts from our junk box.
Onwards and Upwards, Paul
REFERENCE TO QUALI TY
I’m writing to congratulate you and
Doug Malone for the excellent article,
“Build a 0.01% Accurate Voltage
Reference,” which appeared in the Sep
‘07 issue of Nuts & Volts.
As a retired electrical engineer who
did analog circuit design at companies
such as Quantum and Western Digital, I
can readily appreciate the superb design
and clear description that Doug wrote for
your magazine, plus attention to detail
when laying out the board. This is evident
in the stress relief cuts he made in the
vicinity of the reference IC.
Not having any skills when it comes
to soldering surface mount parts, I ordered
two PCBs from Doug with the reference
IC installed. There was a small typo in
the parts list, but an email to Doug
brought a prompt reply with the right
part number.
When the boards arrived and the
additional parts were installed, I was very
pleased to find that the output of the two
reference supplies differed by only 200
microvolts. A truly remarkable achievement considering the cost involved. Back
when I was doing analog circuit design,
it would have cost at least 20 times
as much and required a temperature
controlled oven to obtain similar results.
Phil Kenny
January 2008 97
