Hi I am interested in basic methods used to clamp / shunt voltage and current similar to a regulated power supply but without need for regulation. I prefer primitive methods similar to how a p channel MOSFET can be used for reverse polarity protection.

This is for educational purposes - with a 5v input I would like to clamp any voltage spikes over 5v due to things like motor inductance that might finds its way up the line as well as current clamping at 100ma. I am interested in methods that either cut off the circuit or shunt the excess to ground.

Regards,

 

Most simple Linear-Voltage-Regulators will do what you're asking for.
The one attached here will shut-down any Current over 225ma.
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