I am looking at using two p-ch MOSFETs in series as part of a high-side load switching scheme, and do not understand the following circuit behaviour.
In simulation of the simplified schematic below, no current is driven into the load:
Edit: The MOSFETs being modelled are DMP2008UFG, model supplied by manufacturer
If neither Q1 or Q2 are conducting, Q2 has a floating source voltage and therefore undefined Vgs.
What I expected to happen:
- Q1 to turn on, as its Vgs > Vth.
- As Q1 is on, then Q2's source if no longer floating and is instead defined at near Vcc.
- As Q2's Vgs>Vcc, Q2 conducts
- Current flows into the load
Clearly I am misunderstanding the circuit. Why does no current flow into the load?
Many thanks in advance,