Over on YouTube our hacker [VIP Love Secretary] shows us how to make a simple MOSFET tester. This is a really neat, useful, elegant, and simple hack, but the video is kind of terrible. We found ...

This circuit was designed to meet a medical application’s requirement to drive a laser diode with reasonable precision and a minimum of components and footprint (the device is now in clinical trials).

Calculating the appropriate resistor values for a photocoupler isn’t complicated, but some basic min/max considerations must be acknowledged in when doing the analysis. Determining the resistor values ...