This application note series by Steve Sandler explores the measurement of the dynamic resistance of an LED and how to create a usable SPICE model from the data. Today, LEDs dominate the lighting industry, replacing incandescent, CFL, and halogen bulbs. They are much more efficient at saving power, and as semiconductor devices, they should be much more reliable. Most LEDs are powered by constant current drivers in order to maintain uniform lighting in parallel strings with mat

Oscilloscope users can also calibrate their passive oscilloscope probes, though the process is much less sophisticated and for lack of a better term, wrong.  The calibration process also generally can’t include the “fixture.” This short article shows you what to measure and a method to accurately measure the response of the probe.  In addition to the probe, there are other errors that need to be removed.  Most importantly, this article will show you how to accurately measure

Recently, I used a shielded coaxial cable to measure power supply ripple and the results were even noisier than using an oscilloscope probe. How can that happen? Doesn’t the shielding reduce noise? I even measured my setup using a signal generator and it all looks ok. So what was wrong? On the surface, it seems like a great idea to use a shielded cable to measure noise. In reality, it is a great idea to use a coaxial cable to measure ripple and noise and you can gain the bene