# Question about Diode potential of anode with respect to cathode

#### skyline1397

Sep 13, 2017
3
If I have an ideal diode and I apply -9 V in the anode (P-type junction) and -10 V at the cathode (P-type junction) would the diode become forward biased??
I get that the current-voltage relationship of an ideal diode shows that as long as the voltage across the ideal diode is non-negative i.e. V≥0, the ideal diode looks like a short circuit but the graphs refer to V. Is this V equal to V(anode)-V(cathode)?
Where V potential of anode with respect to cathode

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
12,722
Voltage is always about potential differences. What is the potential difference V(anode)-V(cathode)?
A positive voltage between anode and cathode will make the diode conducting.
A zero or negative voltage between anode and cathode will make the diode non-conducting.

#### dorke

Jun 20, 2015
2,342
Welcome to EP.

You can not apply +1V "on" an ideal diode.
The most possible is 0V,
this will case the diode to conduct ,
the current will be limited by the external resistance.

#### Ratch

Mar 10, 2013
1,098
Welcome to EP.

You can not apply +1V "on" an ideal diode.
The most possible is 0V,
this will case the diode to conduct ,
the current will be limited by the external resistance.

View attachment 36145

You have to have an infinitesimal amount of voltage across an ideal diode for current to be present. Even a copper wire short will not have any current existing at zero volts.

Ratch

#### BobK

Jan 5, 2010
7,682
Which is why ideal diodes do not exist.

Bob

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
12,722
I like to think that the original question was not so much about the behavior of an ideal diode as about the quadrant of the characteristic where this diode would be operating under the given conditions.

Of course an ideal diode doesn't exist and current would be infinite - unless limited by e.g. the limited capabilities of the power sources used.

Replies
5
Views
1K
Replies
8
Views
2K
Replies
5
Views
638
Replies
11
Views
6K
Replies
10
Views
3K