基于模拟电感的二阶状态可调滤波器设计

Design of second-order state-tuned filter using simulated inductance

基于集成运放的主极点模型,首先导出了接地电容双运放模拟电感的等效导纳表达式,它表明只有在理想运放条件下,电路才能等效为一个数值为CR^(2)的电感.以此为依据,并以经典的无源二阶带通滤波器为拓扑,用元件替换法设计了一个二阶状态可调滤波器.该滤波器不仅可实现带通滤波,而且可以实现低通滤波功能.电路仅使用两个集成运放,而且使用两个接地电容,因此电路适宜集成.计算机仿真表明,电路的工作频率高达10 MHz,Q可高达100,并正确地解释了高频情况下出现Q增强和f_(o)减弱的原因.

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 CR^(2).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 f_(o)r 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 f_(o)r Q enhancement and f_(o)weakening under high-frequency conditions is correctly explained.