Amplifiers – With semiconductor amplifying device – Including differential amplifier
Patent
1999-03-24
2000-09-05
Pascal, Robert
Amplifiers
With semiconductor amplifying device
Including differential amplifier
330253, 327307, H03F 345, H03L 500
Patent
active
061149063
ABSTRACT:
To eliminate the offset voltage of a differential amplifier and ensure stable operation even when an input voltage is zero, a settable constant current source and a level shifting circuit are connected to at least one of the non-inverted and inverted input terminals of a differential amplifier. The constant current source produces a constant current that is set according to the offset voltage of the differential amplifier. In one embodiment, the level shifting circuit comprises a pair of depletion mode P-MOS transistors each connected in series to a settable constant current source, the respective series-connected pairs being connected to each input of the differential amplifier. The constant current source has a constant current value that may be varied by trimming using a laser or the like. By setting the output voltages of each such circuit equal, the offset voltage of the differential amplifier is eliminated.
REFERENCES:
patent: 5045806 (1991-09-01), Yan
patent: 5386160 (1995-01-01), Archer et al.
patent: 5467045 (1995-11-01), Tanigawa
patent: 5812005 (1998-09-01), Ezell et al.
patent: 5942936 (1999-08-01), Ricco et al.
Nguyen Patricia T.
Pascal Robert
Seiko Instruments Inc.
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