I'm looking at the Max Vgs spec of N channel Mosfet. Many I'm looking at will say +/- 20V. My question is how I read into the " plus or minus" part of this. For example if I have a simplified circuit with the source tied to Gnd what would be the max voltage I could put on the gate? Would it be 20V or would it the delta of the +/- i.e. 40V? Thanks in advance

 

It is always in the context of the gate voltage relative to the source terminal.

If you have the source terminal tied to ground, then it is still ±20V relative to the source terminal, as well as ground.

If you approach the ±20v limit too closely, you may accidentally exceed it (quite easy to do), which will destroy the MOSFET.

 

I'm looking at the Max Vgs spec of N channel Mosfet. Many I'm looking at will say +/- 20V. My question is how I read into the " plus or minus" part of this. For example if I have a simplified circuit with the source tied to Gnd what would be the max voltage I could put on the gate? Would it be 20V or would it the delta of the +/- i.e. 40V? Thanks in advance

±20V maximum means the voltage must remain with the range of minus 20V to plus 20V.