A previously published Design Idea describes a triangle-wave-driven frequency-doubler circuit employing op amps that produce output frequencies limited to about 20 kHz (Reference 1). This Design Idea ...

This all-analog circuit provides three key waveforms simultaneously and at the same frequency within the audio band. It is useful for evaluating audio systems, transformers, cables, and other ...

1. Gather your kit You'll need LEDs for surface-mount technology -- the small components you see on circuit boards -- to lie flat against your page. And get a power supply too: "Coin cell ...