通过使交流胆抗减至最小,有源滤波器便能解决从加到数字电压表和其它具有高输入阻抗装置上的直流信号中消除波纹的问题。 简单的RC滤波器在这些应用中不是很实用的,因为需要一个大的电容器来衰减波纹。这样的一个大电容器会延长响应时间,而它的漏电流还将大大地加载直流信号。但只要降低交流阻抗,在波纹频率的宽度范围内衰减就能得到改进,进而所需的电容将保持很小。 By minimizing AC choke, the active filter solves the problem of eliminating ripples from DC signals applied to digital voltmeters and other devices with high input impedance. Simple RC filters are not very useful in these applications because of the need for a large capacitor to damp ripple. Such a large capacitor will increase the response time, and its leakage current will also greatly load the DC signal. However, as long as the AC impedance is reduced, attenuation can be improved over the width of the ripple frequency, and the required capacitance will remain small.