low power- high efficiency circuit required

[lawrie]

Has anyone had experience of designing high efficiency low power supply circuitry?
I want a circuit that supplies 1ma at 3.8v Dc for 95% of the time powered from batteries that could deliver up to 12vDc and 5V DC depending on customer requirements. Occaisionaly when the application wakes up it will draw upto 300ma for several minutes with very short duration,(10ms or so) about 1.5A,(GSM pulses)
My current power supply circuit draws 10ma while the application draws less than 1ma and I need to extend battery life by at least 500%
I have looked at some Analog Devices Chips, mainly the ADP range.
Can any one advise what the most efficient device or method may be for this.
Any help or suggestions would be gratefully received

 

[Bung]

Dunno, maybe the electronics guys could help. Power systems tend to deal with bigger Vs and As than this.

Bung
Life is non-linear...