Need Help with Sensefet Circuit for Buck Converter

[jexterbabatugon]

Hi guys,

I am trying to make a simple sensefet design for a buck converter, the problem is that my Vsen amplitude does not vary with respect to the inductor current of the buck.

I have used a Folded Cascode Amplifier (A=91dB BW=8Mhz phase=78) for the OpAmp. Is this enough to be used in the sensing circuit? Can anyone suggest on what may be the problem for my sensing circuit.

 

[Prototyp_V1.0]

Have you tested your Folded Cascode Amplifier indepentently from rest of the circuit?

 

[jexterbabatugon]

Have you tested your Folded Cascode Amplifier indepentently from rest of the circuit?

yes i have independently tested it...I have tested it for the specs above...from what i have read those are the ones i should be looking out for...are there any other reasons why my sensefet won't work?

i attached my sensefet configuration here