| 摘要 |
PURPOSE:To eliminate the necessity for unit parts for forming a low-pass filter and make a circuit system more compact, by forming the low-pass filter for removing reflected noises as an RC active filter whithin the same IC chip for a switched capacitor filter. CONSTITUTION:A filter IC is composed of a clock signal generation circuit 301 for sampling a signal, a switched capacitor filter 302 having a desired transmission characteristics and a low-pass filter 303 for removing reflected noises. In the constitution, a clock signal 311 of sampled frequency is applied from the circuit 1 to the filter 302, and simultaneously, an input signal 312 is applied to the filter 302, and then an output signal 313 including the reflected noises is sent from here to the filter 303 to output as a signal 314 having noises removed. In this case, the filter 313 is composed of an MOS type operational amplifier 401, IC resistors 402, 403 and IC capacitors 404, 405, and the out-off frequency is selected to be a predetermined value. |
