How to provide enough current for my GSM circuit, and still use a LiOn battery?
Option 1: Put the GSM, GPS, and uC chip to sleep in between send/receive events. This is assuming the GSM and GPS chips have a sleep mode.

Option 2: Control power to the GSM and GPS chips via a P-FET. Turn the P-FET on and off with the uC. Except for leakage current through the FET, the GSM and GPS chips will consume zero power when the FET is off. You didn't say what regulated voltage you're using to power the circuit off the battery, so finding a P-FET that has a usable Rds(on) at whatever voltage you're using may be tough. The P-FET will need to pass 2A at whatever Vgs you apply.







simulate this circuit &ndash; Schematic created using CircuitLab

If you explore Option 2, note that if a positive voltage is applied to a pin of a part that is otherwise powered off, current can pass into the protection diodes of that pin and power the device unexpectedly. This might happen if you have a DIO pin attached to the GSM or GPS chip that is driving high when the chips are powered off.