| 摘要 |
PURPOSE:To divide each weighted electrode into a half, drive it by the clock pulse of sampling frequency and give weighted coefficients to the respective divided portions, thereby obtaining required filter output from the sum of signals. CONSTITUTION:Input is sampled at sampling frequency 2fs by switch 14, and outputs from weighting electrodes e11, e21, ..., en1 are weighted by weighting circuits 12-11, ..., 12-1n and added up SIGMA1 to obtain No. 1 output Vout1. Similarly, outputs from weighting electrodes e21, ... en1 are weighted at circuits 12-21, ..., 12-2n and added up SIGMA2 at circuit 31-2 to obtain No. 2 output Vout2. All these output voltages are added up 32 to obtain filter output VOUT. In this constitution, attenuation becomes minimum at 2fs. If transfer frequency, i.e., sampling frequency, is heightened in this way, the accumulation time of electric charges which have been thermally excited decreases to reduce the dark current, thereby making it possible to prevent the quantity of filter input charge from attenuating. |
