Today, i will show the difference in switching noise generated by 2 different diodes (standard 1N4007 vs Schottky 1N5819) in a half wave rectifier circuit when it goes out of conduction. Also shown for comparison is the standard diode with a 100nF snubber capacitor in parallel.

Here’s the circuit used to compare the diodes. A high speed DSO and x10 probe were used to measure the voltage across the diode. The total length for the scope probe tip and ground was less than <1cm to minimize any error.


After the test , we can conclude that a 1N4007 standard diode without the snubber has a higher amplitude of the reverse recovery pulse (which will generate more high frequency noise) compared to the other 2 configurations. The RF content across the AC secondary line (not shown) of the 1N4007 w/o the snubber actually extends beyond 1MHz when viewed from a spectrum analyzer. The bulk of the power is concentrated at 600kHz and below.

Adding a 100nF snubber capacitor across the 1N4007 reduces the diode recovery switching amplitude and increases the pulse width.

When the standard diode was replaced with a Schottky diode, we see a significant drop in the recovery switching pulse level but the width stays the same.