Hi,

I have a few doubts about depletion type MOSFET:


1. The schematic symbol of Depletion type MOSFET and Deletion-Enhancement type MOSFET are the same. Therefore, if any one of them is used in a circuit schematic, how can we distinguish them?


2. For Enhancement type MOSFET, the drain current in two different regions are:


Triode region:




Saturation Region:





What are the drain current equations for a Depletion type MOSFET in saturation region and triode region?


Would you be kind to clarify me the above two doubts?

Thank you.

 

In 95% of a circuit you will see Enhancement type MOSFET. D-MOSFET are very rare device.
Try read this
http://www.ittc.ku.edu/~jstiles/312/handouts/The Depletion NMOS Transistor.pdf
http://www.ittc.ku.edu/~jstiles/312/handouts/A Mathematical Description of MOSFET Behavior.pdf

 

You would have to look at the part number to determine whether the MOSFET is enhancement or depletion.

I believe the equations are the same except Vth is opposite polarity for a depletion mode.