We're using an LM317BTG to power a 4V modem (the LM is connected to a 12V battery). The modem can produce peak currents of up to 2A during transmission bursts. Under normal operations, the modem consumes anywhere between 100mA and 300mA.
We would like to be able to switch the LM317BTG on/off using a microcontroller (digital IOs rated at 5V/couple of mA).
I'm thinking a transistor of some sorts could be used here? I've already used NPN bipolar junction transistor (BJT) (like the 2N2222) to switch low-power devices on/off but I guess I need something more powerful than that?
Do I need to use a MOSFET, or is a Darlington also possible? And how should I hook it up in the circuit? I would like to use a digital IO of the microcontroller (0V or 5V) to switch the LM317BGT on/off.