Abstract: Based on the dominant-pole model of the integrated operational amplifier (Op Amp), the equivalent admittance expression of the simulated inductance using grounded capacitors and dual op amps is first derived, which shows that only under ideal op amp conditions, the circuit can be equivalent to an inductor with a value of CR². Based on that and combined with the classic passive second-order band-pass filter topology, a second-order state-tuned filter is designed by the component replacement method, which can not only realize band-pass filtering but also realize low-pass filtering. With the circuit using only two Op Amps and two grounded capacitors, the circuit is suitable for integration. The computer simulation result shows that the circuit can run up to 10 MHz, and Q can be as high as 100. In addition, the reason for Q enhancement and f_o weakening under high-frequency conditions is correctly explained.

Key words: Q enhancement and f_o weakening, state-tuned filter, simulated inductance, integrated operational amplifier