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EVERYTHING FOR ELECTRONICS
November 2013 7
In his "Build a Headset Amplifier"
article, Ron Anderson explains that
experimenters can make several
errors in building solid-state circuits.
If an experimenter was to try and
make sense of the amplifier
schematic, they would immediately
get confused to see the schematic
symbols of NPN and PNP transistors
are indeed reversed.
I like to remember the transistor
symbols as: NPN — Never Points iN
and PNP — Points iN Permanently
Overall, I did find the design very
instructive, and a bit reminiscent of
the way we did things in the early
1970s. I always enjoy Nuts & Volts!
San Diego, CA
In the text of Ron's October
article, the transistors were marked
incorrectly. These are the proper
Transistors Q1-5 2N5401 PNP
Transistors Q6-9 2N5551 NPN
Transistors Q1-5 2N5551 NPN
Transistors Q6-9 2N5401 PNP
On a Schematic
I enjoyed reading Gerry Shand’s
article in the June issue about the
"Electronic Photocell for Lighting
Control." I like his use of the math
coprocessor; I had not thought of
that before! In the schematic, I have
three questions I hope Gerry can
• Why did you choose the
relatively expensive switching voltage
regulator instead of a common linear
• Why do you employ two
resistors in parallel to limit the current
through each of your LEDs?
• In case of a power outage,
what duration can you expect from
your super capacitor until your time
chip loses the current time?
Judy May W1ORO
Thank you for your questions,
Judy! Here are the answers:
1. I used a switching voltage
regulator in lieu of a standard
Continued on page 60