Answer to No.2

b) Vgs < VTp

A PMOS is turned ON if Vgs < VTp. That is if the Gate-Source bias, Vgs, is more negative than the Threshold voltage, VTp.  Now let us verify it:

• apply logic 0 (blue) to Vin. The PMOS is closed (ON).
• Vg = Vin <= VIL = 1.0 V.  Vs = Vcc = 5.0 V.  Therefore, Vgs = Vg - Vs <= - 4.0 V.
• VTp = - 2.5 V (see lower-right hand box after moving VT a little in the left hand side of applet.)
• So we see that Vgs < VTp when the PMOS is ON.
• This is true for a range of Vin, Vcc, and VTp.