Abstract: A mixed mode biquadratic filter was presented based on fully differential current feedback operational amplifier(FDCFOA). Compared with available CFOA circuits, the proposed filter circuit can reduce total harmonic distortion greatly(THD is 3.6% at 1 MHz of 100 mV input voltage). The FDCFOA filter can realize fully differential input and output voltage mode(VM) and current mode(CM) low pass, high pass and band pass functions without changing circuit configuration simultaneously. The natural frequency can be adjusted independently without affecting quality factor, and the sensitivities are low. PSPICE simulations are completed using 90 nm CMOS technology, theoretical analysis and simulation results verify the availability of the presented circuit.