Active filter stack

Details Active filter stack Active filter stack

1996-10-29

1999-06-15

Pascal, Robert

Amplifiers

With semiconductor amplifying device

Including differential amplifier

330303, 330311, H03F 345, H03F 304, H03F 368

Patent

active

059125870

ABSTRACT:
Active filter circuit 1 consists of five filter stages 70-74 cascoded between a voltage supply and ground potential. The circuit has two major current paths, the first through the collector-emitter paths at transistors 31, 33, 35, 37 and 39, the second through transistors 32, 34, 36, 38 and 40. Each major current path is driven by a current source 61, 62. In operation, a differential input signal is applied to the base electrodes of transistors 31, 32 and a differential output signal is taken from the emitters of transistors 39, 40. The transistors 33, 34 of stage 71 have their collector and base electrodes cross-coupled. Transistors 35-40 of stages 72-74 are connected in the same manner. In another embodiment (FIG. 3, not shown) a cut-off frequency is varied under control of controllable current sources.

REFERENCES:
patent: 3678404 (1972-07-01), Blom et al.
patent: 4514704 (1985-04-01), Curtis
patent: 5225790 (1993-07-01), Noguchi et al.
EDN Electrical Design News, vol. 32, No. 5, Mar. 1986, Newton, Massachusetts, pp. 223-0232, XP002024714, Art Kapoor, et al., "Diverse Circuits Exploit Matching in Quad-Transistor IC".
IBM Technical Disclosure Bulletin, vol. 29, No. 9, Feb. 1987, New York, pp. 3851-3852, XP002024715, "General-Purpose Time-Domain Equalizer".

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