CMOS switched-current biquadratic filters

It is shown how the technique of switched currents (SI) can be used to realize the universal biquadratic transfer function. SI filters require only a standard digital CMOS process, and the power-supply voltage requirement is very low. SI circuits also can be potentially operated at much higher frequencies than switched-capacitor (SC) filters due to the low-impedance nodes of the current mirrors. A simple method to design SI biquadratic filters with maximum dynamic range that leverages the well-established design methodology of SC biquadratic filters has been developed. The methods are demonstrated by designing integrated biquadratic versions of the low-pass, high-pass, and bandpass biquadratic SI filters in a 2-μm n-well CMOS technology