Why diode voltage is 0.7V?

[tiagoft]

Hello, all

Just a question (I have not found an answer for this elsewhere...):

The voltage of a silicon diode is 0.7V. This depends on many factors, including the geometry of the PN junction. My question is: there is a certain range of acceptable values for that geometry. Why the geometry that gives that 0.7V was chosen?

Tiago

 

[Hero999]

Thye voltage is dependant on the temperature, current and materials.

0.7V wasn't chosen, it's due to the band gap of silicon. Germanium has a lower bandgap so the forward voltage is much lower 0.3V.

Here's a link to an experiment you can do yourself.
http://www.phys.csuchico.edu/~eayars/publications/bandgap.pdf

 

[nolram11]

The forward-biased (junction) voltage for silicon diodes is 0.7V in most of the circuit analyses, but it can dip to as low as o.6V because of the construction of diodes is not perfect. As for germanium diodes, yes it's 0.3V when forward-biased.

 

[dlhylton1]

The voltage drop is just based on the material used, not so much the other factors.

Silicon= 0.7v drop
Germanium= 0.3v drop

-David
www.learningaboutelectronics.com
www.allthingsdiscussed.com

 

[V.S.ARJUN]

BECAUSE IT IS ITS CUT IN VOLTAGE .AFTER .7 V CURRENT STARTS FLOWING AND POTENTIAL BARRIER BREAKS