The diode doesn't conduct when it is reverse biased, so it is effectively not present for negative excursions of vo thus negative pulses are not clipped and they remain unaffected.
The input is on the left, the output is the voltage on the right. Maybe it would be clearer if the line marked "—" were to be labelled "ground". https://www.physicsforums.com/images/icons/icon6.gif [Broken]
Please elaborate more, I know that the diode doesn't conduct when it is reverse biased.
Here we have Vi as input voltage, and as you can see in the figure it should be forward biased for positive input voltage, and thus we should remove the negative pulse - not the opposite.
Hmm, probably my question is not very clear, right?
The diode allows the passage of voltage if it is in a way that goes along with the pointer head "arrow like" and this " | " or in other words if "Vp-Vn>0".
Let me post my question in a different way: here if voltage from input passes through the diode when it gives a positive pulse, will it be forward biased or not? And why? With details please.