Question:Electronic Design reader Andrew Frith asks:
"Does anyone know of, or how to make, a signal generator (of sorts) that can produce a square wave output, variable from about 100 Hz all the way up to 50 kHz, and be able to do so in 1- or 2-Hz jumps? Needs to be really stable (obvously), and should have an output of about 200 mA. I'll be running it from a 12-V battery. And the ability to switch from square to sine would be sweet too."
Answers: A recent, perhaps the most recent, issue of Circuit Cellar Ink had a feature article on the subject.
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If you need stability, use a DDS, such as one of the Analog Devices parts. They can be crystal controlled, have sine wave outputs, and some have comparators to make a square wave output.
If you can stand less stability, use a quad op amp to make a "function generator" and tune it with a pot.
Or use a Wein Bridge oscillator.
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