Active filter circuit

Details Active filter circuit Active filter circuit

1990-04-19

1994-05-31

Sikes, William L.

Electrical transmission or interconnection systems

Nonlinear reactor systems

Parametrons

307520, 328167, 330306, H03B 100, H03K 500

Patent

active

053172167

ABSTRACT:
An active filter circuit includes a first and second differential pairs each having a pair of transistors. A capacitor is connected to a collector of one transistor from each of the first and second differential pairs. A first and second negative feed-back paths are connected, respectively, between the collector and a base of one transistor of the first differential pair and between the collector of one transistor of the second differential pair and a base of the other transistor of the first differential pair. By applying suitable voltages to respective inputs of the differential pairs, the active filter circuit functions as a band-pass filter, lowpass filter, high-pass filter, band elimination filter or phase-shifting filter with the same circuit configuration. A current mirror circuit correlatively changes current amounts of the first and second differential pairs in response to a control voltage, whereby a filter characteristic can be changed.

REFERENCES:
patent: 3969682 (1976-07-01), Rossum
patent: 4377759 (1983-03-01), Ohhata et al.
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patent: 4818903 (1989-04-01), Kawano
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patent: 4859881 (1989-08-01), Yamamoto et al.
patent: 4968901 (1990-11-01), Shacter
patent: 5023491 (1991-06-01), Koyama
"A Fully Integrated Filter Circuit For VCRs", T. Fukuda et al, IEEE Transactions on Consumer Electronics, vol. CE-32, No. 3, Aug. 1986, pp. 644-650, New York.
"Automatically Tuned Filter Uses IC Operational Amplifiers", G. J. DeBoo et al, EDN/EEE, vol. 17, No. 3, Feb. 1, 1972, pp. 38-41, Denver, Colorado.
Denshi Gijjutsu vol. 22 No. 4 (Apr. 1980) Published by Nikkan Kogyo Shinbun Sha.

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