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分路滤波器广泛地应用于电话多频系统中。本文提出一种能实现这种滤波器的“GIC”导出式带通电路,这种电路的无源、有源灵敏度都是很低的。但是,当滤波器的增益大于2时,“GIC”导出式滤波器由于运算放大器的有限增益带宽乘积,有Q增大的缺点。现提出一种补偿设计法,能大大地改善滤波器对所有增益的特性,并详细给出了实验结果和分路滤波器的设计实例。实验结果同理论分析是一致的。
Shunt filters are widely used in telephone multi-frequency systems. This paper presents a “GIC” derived bandpass circuit that implements this filter. The passive and active sensitivity of such a circuit is very low. However, when the gain of the filter is greater than 2, the “GIC” derived filter has the disadvantage of increasing Q due to the finite gain bandwidth product of the operational amplifier. A compensation design method is now proposed, which can greatly improve the characteristics of the filter for all gains. The experimental results and design examples of the shunt filter are given in detail. The experimental results are consistent with the theoretical analysis.