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Synth VCO

A synthesizer voltage controlled oscillator based on a 1980's issue of Electronic Design

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A VCO based on a schematic I found in an old magazine article titled "Inexpensive voltage-controlled oscillator is rich in harmonics over entire audio range". I built a breadboard version during a Hackathon in 2016, then decided to finish it.The magazine article circuit had two flaws in it. The 555 timer was hooked up wrong to be a schmitt trigger and the BJT invertor had a resistor in an incorrect position. I replaced the 555 timer + bjt with an op-amp to simplify things.When debugging the original circuit, I found it really helpful to seperate each circuit block and feed dummy signals into them. I kept that in the PCB as well with the three jumpers.I did an algebraic analysis of the integrator because it's non-intuitive why switching in that resistor would reverse the output. It's uploaded in the Files section of this page.

Adobe Portable Document Format - 798.21 kB - 08/18/2020 at 23:41

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Adobe Portable Document Format - 104.64 kB - 08/18/2020 at 21:56

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Portable Network Graphics (PNG) - 143.16 kB - 08/18/2020 at 21:56

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Portable Network Graphics (PNG) - 104.74 kB - 08/18/2020 at 21:56

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