Generally i place mosfet with Source connected to ground and do negetive switching. But i am coming across a problem when there will be circuitry after ground.(So i cannot connect my Mosfet Source to ground)
I see people put a diode. Is it the solution, Please verify
This is the problem
Can this be its solution .
Also comment if there can be better design for this.
ok i have just modeled Switch with some external circuits which can be in high impedance state.
Just because the source is in high impedance state and i need ground to create Vgs , to ON the mosfet.
My problem is i dont get ground due to high impedence circuit.
I see in google people use diode in similar circuit.
- - - Updated - - -
i have just modeled Switch with some external circuits which can be in high impedance state.
- - - Updated - - -
Yes sure, I am considering that.
Please dont look into resistor values, i have not labled that correctly as of now
The only thing that protects a power MOSFET gate
from high drain voltage, is the depletion region of
the D-B (B=S) junction. If there is no stiff source
potential then the gate oxide will see full D-G voltage
and pop.
A reverse biased diode helps none. The source relative
to gate potential must hold position. If you want the
pushbutton to interrupt current, put in the drain leg
(if switch has tolerable isolation for safety etc. - if
not, use pushbutton to control a NO relay perhaps).