Patent ID: 7999608

Claim:
A filter system comprising: an LC notch filter, wherein losses associated with the notch filter are modeled by a resistance; and a Q-enhancement circuit coupled to the LC notch filter, said Q-enhancement circuit configured to generate a negative conductance so as to at least partially compensate the resistance in the notch filter, wherein the Q-enhancement circuit comprises a differential pair circuit, the differential pair circuit is configured to provide the negative conductance as an adjustable negative conductance responsive to a bias voltage, wherein the bias voltage is coupled to gates of a pair of transistors to supply a bias current to the differential pair circuit, wherein the differential pair is a MOSFET pair and the Q-enhancement circuit further comprises a local feedback circuit coupled between a first transistor of the MOSFET pair and a second transistor of the MOSFET pair and configured to linearize a square-law response characteristic of the MOSFET pair.