CAPACITOR CHANGING TYPE BI-QUAD CIRCUIT BLOCK HARDLY INFLUENCED BY CHANGE OF GAIN AND CAPACITANCE RATIO OF OPERATIONAL AMPLIFIER AND FREE FROM CONTINUOUS FEEDBACK

摘要

PURPOSE: To prevent a circuit block from being affected by the gain change of an operational amplifier by constituting the circuit block to provide a prescribed filter function by selecting sensitivity for the change in the gain of the operational amplifier by controlling a two-position type switch. CONSTITUTION: This biquadratic circuit block is provided with operational amplifiers OA1 and OA2, capacitors C1-C8 and plural switches corresponding to a clock signal H. These switches are composed of a 1st switch group, to which a subscript (e) is added, and a 2nd switch group to which a subscript (o) is added. The 1st (2nd) switch group is opened (closed) during the 1st half cycle of respective cycles of the clock signal and closed (opened) during the 2nd half cycle of respective cycles. Besides, this circuit block is provided with input/output connecting terminals P1-P6 and when any connecting terminal for impressing signals to be filtered and any connecting terminal for collecting the filtered signals are selected, different filter functions can be provided. Further, two-position type switches 46, 48, 50 and 52 are provided and any prescribed switch function can be provided through selection.