Performance comparison of Tow-Thomas biquad filters based on VOAs and CFOAs

Tow-Thomas biquadratic filters implemented using Voltage Operational Amplifiers (VOAs) and Current Feedback Operational Amplifiers (CFOAs) are analyzed and compared. Starting from the non-idealities of Miller integrators deriving from practical limitations of VOAs and CFOAs, the pole frequency and the Q-factor deviations of the filter have been predicted paying special attention to the high-frequency operations approaching opamps gain-bandwidth product. Despite the inherent high-speed potential of CFOAs, the associated implementations have in general lower parameter accuracy and increased tendency to instability. To verify theoretical derivations, SPICE simulations have been performed and found in remarkable agreement with expected data.