Answer to No.2
a) Enhancement mode
A p-channel MOSFET transistor is Normally-OFF (enhancement mode)
if its threshold voltage, VTp, is a negative
value. You can verify this by adjusting the VT
in the right-hand side of the applet and observing its value in the lower-right
- A MOSFET device is normally-OFF if the device is OFF at zero gate-source
bias (Vgs = 0).
- A p-channel MOSFET is ON if Vgs is more negative than VTp
(i.e., Vgs < VTp ).
- Thus if VTp = -2.5 V (a negative voltage),
then the PMOS is OFF at Vgs = 0 V because Vgs > VTn,
and thus it is normally-OFF.