Thanks all, looks like a P-Channel plus BJT is the answer...

It doesn't, but the OP says it did.

78L05 can't regulate with a quiescent current of less than 3-5mA and a load current of at least 1mA

Well, it works in terms of measured voltages when the MOSFET is turned on but not when the MOSFET is off. It also doesn't work in terms of driving the load.

 

Well, it works in terms of measured voltages when the MOSFET is turned on but not when the MOSFET is off. It also doesn't work in terms of driving the load.

That's because the regulator can't regulate without a path for the quiescent current. When the MOSFET is off, the output of the regulator won't be regulated.

 

Use a regulator with an enable pin!

 

If you use an LM317 regulator to generate the 5V, then pulling the ADJ pin to ground with an N-MOSFET will reduce the output to 1.25V, which, for powering a typical electronic load, can often be considered essentially off.

 

So, I dug up a 7805 model and ran the sim again and in fact did not get the results I expected.

At the lower input voltages 8 to 10 volts, the voltage actually dropped at the output, but above 12 volts or so the voltage output increased.

And since I always use 12 volts or more as the input on my 5 volt regulator projects I made a false assumption. (that output voltage would also increase at lower input voltages)

So of course, I had to breadboard the circuit and the results were pretty close to the sim. (using a brand new modern LM7805)

The output voltage was aprox 3 volts when lifting the ground pin and the input was 8 volts.

When the input was much higher than 12 volts the output was well above 5 volts.

So, I learned something today.