The secret sauce is in component selection and tuning. Opengeiger uses the BPW34 diode because it is relatively common and has a large surface area, but also because it has a very low capacitance ...

also known as a Shockley Diode, is a crystal made of alternating layers of N- and P- type semiconductors. By putting in four layers, instead of the three used in transistors, the Shockley Diode ...

Then knowing he needed 4 mA to power each LED for backlighting he used some 1978 vintage current limiting diodes designed to pass 2mA each regardless of voltage source, within limits of course.

In this module, you will learn the fundamental operating principles, design, fabrication techniques, and applications of two of the most widely used light-emitting devices in the world today - ...