PURPOSE: To decrease capacitors in number even when variable kinds of filter characteristics are increased and to facilitate integration and realize a weighted filter coefficient in binary notation by using a programmable integrator consisting of an integral capacity, switch, weight coefficient generator, etc.
CONSTITUTION: When switches SW3 and SW4 are turned on by a sampling clock ψs, an integration circuit in a figure A holds an input voltage by a sample holding circuit 2, transfers the voltage by turning on SW5 and SW6 at timing whose period is shorter than that of the clock ψs by turning on switches SW5 and SW6 by signals of weight coefficients of respective digits of a digital value from a weight coefficient generator 3, and adds the output voltage of an operational amplifier 1 to the output voltage up to the point at the ratio of capacitance CA' and capacitance CB to operate switches SW7 and SW8 at the same timing with the generator 3; capacitance CB' is connected in parallel to C-B or grounded at both terminals to discharge the capacitance CB' to the reciprocal of the capacity sum of capacitances CB and CB', and when the SW4 is turned on, a voltage with a specific integral constant is outputted. Integrators (a)∼(d) of the filter circuit in a figure A are weighted by a weight coefficient generating circuit 4.
KANEKO KAZUHIRO
UENO NORIO
