diode cut in voltage

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p11

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plz some one explain me that why we see 0.7 volt fixed across diode even if we increase the voltage across it . i mean , 0.7 volt is the barrier potential.so it should decrease with increase in forward voltage , but we see 0.7 volt fixed no matter how much we increase the forward voltage . why ?

KlausST

Super Moderator
Staff member
Hi,

did you use a series resistor with the diode?
Or a current limiter?

Klaus

p11

Banned
yes i have connected series resistance .......

crutschow

The diode forward voltage is not constant, it varies logarithmically with current. It's just that at typical operating currents the voltage is around 0.7V.
Here's a example of the voltage versus current of a diode. Plot 2 shows the log relationship.

p11

p11

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