| 摘要 |
PURPOSE:To change a band pass frequency or a cut-off frequency automatically and periodically, by providing a current control means periodically changing a current flowing to an integral network so that the pass frequency band can be changed periodically. CONSTITUTION:In place of conventional variable resistor for bar code type active filter, analog switches AS1 and AS2, and resistors R4 and R5 are used. By controlling the ratio of the on/off time of the switches, a current flowing to the 1st integral network consisting of capacitors C1 and C2 and the 2nd integral network consisting of the capacitor C2 and an operational amplifier OP1 can be controlled. The band center frequency can be changed periodically by periodically controlling the on/off time ratio of the switches AS1 and AS2. |
