| 摘要 |
PURPOSE:To decrease the number of parts by varying the resistance value of one optional resistance among series resistances, constituting a filter by short-circuiting it by an analog switch. CONSTITUTION:When a control voltage at a control input terminal 3 is held at a high or low level, analog switches S1, S3, S5, and S7 turn off or on and when a control voltage at a control input terminal 4 is held at a high or low level, analog switches S2, S4, S6, and S8 turn off or on. For this purpose, the control voltages applied to the control input terminals 3 and 4 are controlled to vary resisstance values, thereby varying characteristics of a filter. |
