# diode cut in voltage

Status
Not open for further replies.

#### p11

##### Banned
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

##### Advanced Member level 5
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

Points: 2