Patent ID: 8447275

Claim:
A tunable complimentary filter for measuring current through an inductor in a switch-mode power supply (SMPS), comprising: an operational transconductance amplifier (OTA) having a first input coupled to a voltage source side of an inductor in a switch-mode power supply (SMPS), a second input coupled to a load side of the inductor and a current output; an operational amplifier configured as a buffer amplifier and having an input coupled to the current output of the OTA; a first adjustable resistor coupled between the current output of the OTA and a return of the voltage source; a second adjustable resistor having a first end coupled to an output of the operational amplifier; and a tuning capacitor coupled between a second end of the second adjustable resistor and the return of the voltage source; a voltage from the tunable complimentary filter is available at the second end of the second adjustable resistor, wherein the voltage is representative of the current flowing through the inductor of the SMPS.