Ampliifer with a stable gain upto 500khz needed

[vinayakdabholkar]

Need a opamp with a stable gain upto 500khz to sense the voltage across the sense resistor in a synchronous buck converter
The specs are Vin=12
Vout=1.2V
Iout=12A
Fsw=500Khz
Rsense=10m ohms
Please help

 

[chuckey]

out of idle curiosity, why are you sensing the ripple current and not the smoothed DC current?
Frank

 

[vinayakdabholkar]

out of idle curiosity, why are you sensing the ripple current and not the smoothed DC current?
Frank

I had thought the ripple current is directly given as a ramp to the pwm comparator, so that a separate ramp wont be generated.
Another thing that i had tried was sensing the inductor DCR current by using a RC in parallel with it and matched the time constants L/DCR to RC so that voltage across DCR is equal to voltage across Capacitor. But could not figure out how to go foward with it to get the average current.

 

[chuckey]

I see your point. However I think that you might have a problem getting a .01 ohm resistor rated at >12A and being non-inductive at 500KHZ. Best of luck
Frank

 

[vinayakdabholkar]

Can any operational amplifier be connected across the sense resistor in a differential amplifier configuration with unity gain to sense the voltage and convert it into a single ended one and then use a resistor to sense the current ?