Tunable Biquad Filter Circuit Including Phase Shift Detection and Methods for Using Such

A method for tuning a biquad filter, the method comprising:

• providing a biquad filter circuit having an adjustment input;
• providing a transconductance circuit having a gain input;
• providing a reference voltage to the transconductance circuit, wherein the transconductance circuit provides an amplified output corresponding to the reference voltage multiplied by a gain controlled by the gain input;
• modifying the gain input until the amplified output is approximately equal to the reference voltage;
• providing a calibration input to the biquad filter circuit, wherein the calibration input exhibits a frequency, and wherein the biquad filter circuit provides a filter output;
• mixing the filter output with the calibration input to yield a product, wherein the product includes a static component and a time dependent component;
• and
• generating the adjustment input based at least in part on the static component.