lately i was analyzing a simple circuit with 2 MOSFET, 1 Nmos and 1 Pmos, where the Nmos was acting as a switch and its drain was connected through a resistance to the Pmos' gate. The pmos had it's source connected to a positive reference voltage and it's drain connected to a load. Between the Pmos' gate and drain a capacitor was placed.
Now, i was trying to get the circuit polarization but to me, when no signal is applied to the Nmos' gate, the Pmos should have its gate floating.
But in reality it seems that that Pmos should actually be turned off and not on.
Am i not considering some aspects of a 'real-life' MOSFET for this?
Thanks in advance.
EDIT – Here's the schematic:
Best Answer
What is likely to happen is that you create a latch. The n channel fet turns on and charges the capacitor. This activates the P channel fet. If the n channel is turned off, the cap remains charged and the P channel fet remains activated.
However, over time, the cap may slowly discharge and the P channel fet will gradually turn off. There is no other mechanism in your circuit for turning the P channel fet off. Basically, as it stands, I would describe it as a flawed circuit.