I pulled an old computer power supply apart and salvaged a bunch of parts. One of them is a GBU806 bridge rectifier.
Wanting to learn about these things and play with my new toys, I hooked up a signal generator to the input, and my scope to the output and was able to see the half wave.
As I played with the frequency, I noticed that it got to a certain speed where the minimum voltage wouldn't go down to 0 on the scope, but the maximum would essentially stay at the peak (5 V input normal went to 2.25 V peak, eventually went down to 2.20 V).
So I assume the rectifier wasn't switching as fast as the signal, right?
What I'd like to know is how to read the datasheet so I would know the operating frequency of this rectifier, and perhaps "predict" the minimum voltage at a specific frequency. Is that possible?
I was using a Sine Wave, at 5 v P-P. Min voltage started to become non-zero at around 320Hz.
Here is the datasheet:
https://www.diodes.com/assets/Datasheets/ds21227.pdf
Adding a resistor on the output did the trick. Here's a before/after waveform. This one is 4V P-P Sine wave, at 3kHz. Interesting drop right after the crossing:
Best Answer
Perhaps parasitic capacitances are acting as a smoothing capacitor would, storing charge, in the classic bridge and cap setup:
simulate this circuit – Schematic created using CircuitLab
As source frequency increases, the time between peaks of the rectified output decreases, and whatever measuring equipment you have connected across that output has less time to discharge that capacitance.
In fact, the measurement device (an oscilloscope, with 40pF input capacitance?) may be the very capacitance preventing the output voltage from discharging to zero quickly enough.
Therefore you see the output never returning to zero, unlike the classic full-wave rectified signal we are shown in school.
A good way to test this idea is to connect a resistive load across the DC output of the bridge, which would discharge any capacitance there, but not so small as to overload the source signal generator. A 1kΩ across the output would be probably be fine.
In any case, I suspect the maximum frequency of operation of this setup will be more a function of load impedance (including any capacitance, explicit or parasitic) and source impedance, than the speed of the rectifier diodes themselves.