Switched-current filter models for frequency analysis in the continuous-time domain

A simulation and modeling methodology for switched-current (SI) filters is described, and some results are presented. These results, which differ from the response that a true sampled-data filter would predict from z-plane analysis, demonstrate the need to investigate the complete response of an SI filter to a continuous-time input waveform. It is shown that current mirrors with a large g_m:g_o ratio are required for SI filters, and that the stopband response of many SI filters is strongly dependent on the sampling time of the input sample-and-hold circuit