| 摘要 |
1323918 Active filters INTERNATIONAL BUSINESS MACHINES CORP 19 April 1971 [16 April 1970] 25604/71 Heading H3U A bandstop filter comprises a current node E<SP>1</SP> to which are connected: a series connected resistor R1 and commutated network BPF arranged to block current I in a frequency band centred on the commutating frequency; and a current generator GEN controlled by the filter input signal E. The commutating signal may be derived from the input signal as described in Specification 1,323,917. The resistor and device may be connected in the feedback circuit of an amplifier OA, T1 the output from which is coupled to a pair of output transistors in unit GEN. A current bias circuit CT is also coupled across the feedback path. |
