Floating ground when mosfet is off - is this a good design choice?
Disconnecting (part of the) ground to switch on/off your circuit is really asking for trouble.

It is a really really bad idea.

Also, it will very likely not work and result in unexpected behavior.

For example: there are ESD diodes between all pins of all ICs. In the AMS1117 circuit, there will be a diode between pin 3 (out) and 2 (adj) of the IC. This diode will conduct when you want to switch the circuit off. So the circuit will not be off even when you think you're switching it off (by disconnecting the ground). There will still be a connection to ground via an ESD diode and that will be supplying power to your circuit.

This is just one of the reasons that no sane designer does this.

Instead what experienced designers do and what has been proven to work (these solutions are used in all your gadgets) is:


Use enable/disable pins on ICs that have them.
If your regulator does not have an enable pin, use a different regulator.
In some cases using a PMOS in series with the positive supply rail (not ground) can work, but you need to be careful. Take into account all ESD diodes that are in all ICs, watch this video to learn more.
put microcontrollers etc. in standby / low power mode, there is no need to disconnect the supply if you configure a uC properly.