I need to use a linear regulator to get an output with low noise <1mV, but the output needs to vary between 0-5V@2A So I was thinking that I could use a dcdc on the input of the linear to reduce power by only having the minimum amount of head room. Are there any parts or circuits that would allow me to do this. Vary the linear from 0-5V and then vary the dcdc to maintain the mimimum head room of the linear.
Thanks