Category Archives: opamp

A 38-Year-Old Vocoder Project

It is hard to remember that scant decades ago, electronic magazines — the pre-Internet equivalent of blogs — featured lots of audio circuits based on analog processing. Music synthesizers were popular for example, because microcontrollers were expensive and unable to perform digital signal processing tasks in the way you would use them today. [Julian] has been trying to build a vocoder from that era from ETI magazine. Along the way, he’s making videos documenting what he’s found and how’s he resolving issues.

The circuit generates levels for particular input frequencies. It does so with a two-op-amp bandpass filter, a two-op-amp …read more

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Posted in classic hacks, eti magazine, opamp, opamp filter, vocoder | Leave a comment

About Schmitt (Triggers)

There is an old saying: “In theory, theory and practice are the same. In practice, they are not.” We spend our time drawing on paper or a computer screen, perfect wires, ideal resistors, and flawless waveforms. Alas, the real world is not so kind. Components have all kinds of nasty parasitic effects and no signal looks like it does in the pages of a text book.

Consider the following problem. You have a sine wave input coming in that varies between 0 V and 5 V. You want to convert it to a square wave that is high when the …read more

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Posted in hysteresis, op-amp, opamp, schmitt trigger | Leave a comment