View Single Post
  #43  
Old 06-10-2010, 04:57 PM
bojan's Avatar
bojan
amateur

bojan is offline
 
Join Date: Jul 2006
Location: Mt Waverley, VIC
Posts: 7,112
Quote:
Originally Posted by mswhin63 View Post

An example when I did my aprentiship was to suggest Diode blocked half an AC waveform in a single direction, this was mainstream at the time. I felt along with another person at the time that a diode was harmonic generator that produced so many harmonics that it appeared to block. It turned out few years later that it was partcially true as it was easily proven by placing a band pass filter after the diode and re-creating the waveform minus a small distortion.
Malcolm.
Both models of a diode you are mentioning are actually accurate.
The difference is in mathematical analysis.
One model (blockage of current in one direction) is more applicable to low frequencies, including DC.

The other one (harmonics generator) is more suitable for higher frequencies ....
However, the full mathematical model predicts that because diode has a very non-linear u-i characteristic (meaning, it passes current in only one direction), it will generate higher harmonics.. and their sum will result in waveform showing only one half-period.

I think your example is not a good one... it only shows the difference in approach (simplified apprenticeship level versus comprehensive uni level).
Reply With Quote