I've noticed that in all resources on diodes and rectifiers, they show the output voltage as the positive half-wave of the input signal. However, that seems wrong.
I understand that there's a voltage drop across the diode, and if the total voltage is below this level, the diode is closed. Therefore, it'd only seem logical, if the diode didn't open right away, but only after the input wave reaches this voltage.
Here's my illustration – first, input. Second, my idea of output. Third – output as shown in textbooks.
If I am wrong, how is it possible that there's no "flat area" in the output signal, when the input is below the diode's opening level?
Best Answer
Yes, you are right, have a look at this ltspice simulation of a simple full wave rectifier (click to enlarge):
Textbooks like to simplify things before they go in depth (if at all). How many text books have you seen to talk about diode drop at that point at all?
Its an application of wittgensteins ladder.
Note that at higher frequencies things like the diodes recovery time will start to play an important role too, but even less textbooks talk about that. Both things are not immediately important to understand the concept that should be learned at that point.