Nuts and Volts - November 2013

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EVERYTHING FOR ELECTRONICS November 2013 7

Transistor Twister

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!

Robert Trescott San Diego, CA

In the text of Ron's October article, the transistors were marked incorrectly. These are the proper specs:

Correct: Transistors Q1-5 2N5401 PNP Transistors Q6-9 2N5551 NPN Incorrect: Transistors Q1-5 2N5551 NPN Transistors Q6-9 2N5401 PNP

Shedding Light 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 component?