A battery driven mobile communication device drawing a base current with periodic high current pulses during transmission. The current pulses may be larger than the current level which the device's battery can supply. The device uses a switched mode power supply with an output capacitor sufficiently large to provide the high current pulses when demanded by the load, without its voltage falling below that necessary to operate the device. This power supply provides the average current drawn by the load, and maintains the capacitor's charge. When the load demands a current pulse, that excess current is drawn from the capacitor, which begins to discharge. Once each pulse is completed, the battery continues to provide the lower baseline current of the device, and at the same time tops up the capacitor to replace the charge used during the pulse. The battery may be a low cost primary battery.