i'm facing the problem to turn a 9V (battery) powered device OFF using the output of a 3.3V based microcontroller. To do this i already threw together the following circuit (which works - assuming i drew it correctly...) EDIT: oops, the pulldown resistor R5 should of course not be 220ohms but something bigger.
The device I have to switch off is represented by LED1 and the digital Output from the microcontroller by switch S1. The problem this circuit gives me is the high voltage drop of about 1V which would probably toggle the device to battery-low mode. Is there any alternative circuit i can use that has a very low voltage drop? And also, the design should be "fail safe", so the microcontroller could die/become unresponsive/whatever and in most cases the device will still be functioning like in my example above. Thanks