depletion region wider with reverse voltage...

[sohail qureshi]

hi experts............my question is HOw the depletion region becomes wider , when we increase the reverse biased voltage in JFET............tnx

 

[Raza]

Hi,
Here is a good lesson on FET's operation.
**broken link removed**

 

[dick_freebird]

You can think of it this way - the device naturally has some
quantity of fixed charge from the dopants. In the junction
region there is a built-in potential which separates the charge
for some volume (the zero bias depletion region). If you
increase the reverse potential you separate more charge
and since charge per volume is roughly fixed, increase
the charge-less volume by increasing the distance
(depletion width).

When that becomes untrue, like if you get backed up
against a higher doped feature, the distance won't
move anymore and field goes up instead. Then you
get ionization, avalanche and break down.