I have a voltage regulator circuit that works great till the voltage falls below 5V. I want to turn this FET into a Schmidt trigger to turn the power off and on, the voltage regulator circuit. Any suggestions? My voltage regulator circuit draws .150amps.

 

Did you mean 150ma? Is this homework?

 

Did you mean 150ma? Is this homework?

 

no it's not homework.
Yes, 150 ma.. I found this circuit that I think will work. But I want the output low when the input goes low. I wonder if I substitute PNPs, if it will work?

 

Have you used protoboards before? There is a circuit a previous member named @THE_RB created to comes close to what you wanna do with a little bit of modification.
https://romanblack.com/smps/smps.htm

 

If the Vx is less than 2.5V so the Vcc is less than 5V all transistors and mosfet are turned off.
The 47k sets the hysteresis.
The red led serves as 1.8V reference so together with pnp Vbe (0.7V) the pnp will compare the Vx with 2.5V.
Use low power led that is bright at 5mA.