Diode voltage drop and noise

[fonograph]

Does the amount of voltage drop in diode affects how much noise it adds to the signal? Does more voltage drop means more noise?

What type of diode have lowest noise,shotky? PIN ? Tunnel diode ? Gun diode?

[Kleinstein]

Usually the voltage drop on a diode is considered relative low noise. For the white noise part the differential resistance is relevant parameter. For the ideal diode this is  kT/e  / I - and thus independent of the diode. Real diodes usually have a slightly higher resistance. So already at 1 mA the resistance is in the 50 Ohms range and thus a white noise level of only 1 nV/Sqrt(Hz) is expected. In the high frequency region, so that the diode is considered slow, the differential resistance is even lower - thus slow PIN diodes can be even lower noise above some 100 kHz.

There might be some additional 1/f or similar low frequency noise contribution. Just from my feeling and picture of how a diode works this is expected to be higher in diodes that are slow and have a higher forward voltage / low leakage. Not much of this is expected for fast gold doped diodes like the 1N4148.

Current noise, for the reverse leakage is a different thing. Here charge quatisation gives a major noise contribution, thus again diode type independent - it only depend on the leakage current.

[danadak]

These might help -


http://qucs.sourceforge.net/tech/node68.html#SECTION001123000000000000000


http://rfic.eecs.berkeley.edu/~niknejad/ee142_fa05lects/pdf/lect11.pdf


http://www.ece.ucsb.edu/Faculty/rodwell/Classes/graduate_noise_class/noise_notes_set7_new.pdf     pages 21,22


Regards, Dana.