3V high-frequency current-mode filters

A fully differential current mode integrator circuit and its cascode variants are presented for use in low voltage, high frequency signal processing applications. It is shown that good linearity is achieved with signal levels up to the current bias, the equivalent of voltage mode rail-to-rail operation. It is also shown that low (voltage) bias levels actually improve linearity (within the strong inversion region of operation), enabling bias levels to be designed low enough for the integrators to work at 3V supply voltages. Major frequency response barriers are eliminated because the basic integrator has by design no parasitic poles, which enables the frequency of operation to scale much higher than previously practical. The design, fabrication, and characterization of a test filter demonstrated the feasibility of the approach