Make: Analog Synthesizers

Appendix A. A Field Guide to Op Amp Circuit Applications

In this appendix, I’ll present a number of useful analog synth circuit building blocks, including inverting and noninverting buffers, comparators, integrators, and digital-to-analog converters. For each circuit element, I’ll present the schematic and explain how the circuit works. Many of these circuits have generally useful functions that can be put to work in your synth-DIY work, as well as your electronic projects.

Buffers

Here are some circuits you can use when you need to boost the level of a signal. Typical op amp outputs can only source or sink about 4 to 5 mA before the output begins to degrade and distort. When driving LEDs with an op amp, this current drive limit isn’t a big deal, ...