Saturday, September 5, 2020

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LM358 triangle and sine wave generator

Not content with a simple LM358 square wave generator as seen on the last blog, I look this week at converting the square wave to other wave forms using the mathematical functionality of OpAmps. Casting about in the shallow end of the internet pool, I happened upon this variation of the previous circuit.

After lots of playing about on iCircuit and some deeper internet trawling, I was able to make the circuit work on a simulator as follows.

It was a little concerning that the signal degrades in voltage over the three opAmps, such that the final voltage fluctuation is only around 2V from a 9V supply. I tried to rope in a transistor to amplify (with no real success) but I'll keep trying to amplify the signal - probably with the "free" side of the second opAmp maybe something like the following:

The final (simplified) design, using only 10k resistors and 10uF capacitors, looks a treat "In Real Life" and it functions (pun intended) as designed!



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