I need to power a 3.3V 400mA signals from uno digital output pins 10-14, any circuit that might work?
Even without paying attention to the 3.3v voltage, no circuits will help you to power a load of 400 mA from the Uno pins, since each pin is rated for a maximum of 40mA.
Use an external power supply instead and control it via mosfets or relays
Exactly, I have external power supply 3.3V up to 2000mA,
I need the easiest way to control the signal without disturbing the 40mA uno digital output.
It maybe be mosfet, it does not help that the voltage is lower on high amp side.
The 40mA rating is a stress rating and not a working rating. The data sheet says prolonged operating at the stress level will cause damage.
Correct it dose not help. The simplest way is to use a logic level FET and an external power supply. With your load between drain and power supply. At these sorts of currents you could also just about use a transistor as well.
What's the load?
A logic level MOSFET may do the job, else an H-bridge might be required.
"The simplest way is to use a logic level FET"