0
\$\begingroup\$

The depletion mosfet can also operate in enhancement mode when the gate voltage is positive (say for depletion type NMOS).

My question is :

Will the Shockley equation be still valid in the enhancement mode? or Should we use the equations of enhancement NMOS?

Moreover, if i am driving the depletion type MOS to a an enhancement type MOS under a constant drain source voltage (Vds), say for example:

enter image description here

In the above case, Vgs is positive and the depletion type MOS is in enhancement mode also Vds > gate voltage ,Does that mean the Depletion MOS is in saturation region of the enhancement mode?

If i neglect Vds here and use current equations of NMOS enhancement type , i get:

Resistance =500 ohms.

But am confused about whether its correct or not and if that's the case why should i neglect Vds ?

\$\endgroup\$

1 Answer 1

Reset to default
2
\$\begingroup\$

The only difference between an enhancement mode NMOS and a depletion mode NMOS is the value of Vt for which Id = 0, the formulas are the same.

If you understand how an enhancement NMOS works you could just imagine it having a voltage source in series with the gate and the total will behave as a depletion NMOS !

\$\endgroup\$
2
  • \$\begingroup\$ i agree with Vt thing but are the formulas actually same? depletion mosfet is more like jfet when you try to deplete channel out and shockley's equation is used !! \$\endgroup\$
    – Ashik Anuvar
    Commented Nov 23, 2015 at 12:52
  • \$\begingroup\$ Also i wont to know whether for the given Vds and Vgs the depletion mos is going behave like a enhancement mode mos in linear region or not ?! \$\endgroup\$
    – Ashik Anuvar
    Commented Nov 23, 2015 at 12:53

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.