ACTIVE PIEZOELECTRIC FILTER Russian patent published in 2003 - IPC

FIELD: radio engineering; frequency selection of signals. SUBSTANCE: filter has first and second operational amplifiers 1 and 2; first through eighth piezoelectric resonators 3, 4, 10, 11, 14 through 17; first through tenth resistors 5 through 9, 12, 13, 18 through 20. Piezoelectric resonators 14 and 15 are connected in parallel to piezoelectric resonators 3 and 4 and are inserted between input potential terminal of filter and resistors 5 and 6, respectively, connected at inputs of operational amplifier 1. One output of operational amplifier 1 is connected to first output potential terminal of filter through series-connected piezoelectric resonator 10, resistor 12 and through operational amplifier 2, piezoelectric resonator 11, and resistor 13. Other output of operational amplifier 1 is connected to second output potential terminal of filter through series-connected piezoelectric resonator 16, resistor 18, and through inverter built around operational amplifier 2, piezoelectric resonator 17, and resistor 19. EFFECT: enlarged functional capabilities due to using two frequency-separated passbands. 1 cl, 1 dwg