http://www.geofex.com/Article_Folder...rot/dcprot.htm

Here they hv suggested to use mosfet in place of relay. Now there r three pictures of circuits.
I want to use mosfet configration from circuit 1 with mosfet driver circuit from circuit 3. but i want to use single power supply.
Most interesting part i want is : i want to use this as speaker protector. Hence first the mosfet will conduct full.
then as the driving circuit voltage increases the current through the mosfet switch must reduce. So during overload
mosfet will work like bulb protector i.e. it will conduct less.
Is this possible?
If yes, then guide me how to do this?