Amplifiers – With semiconductor amplifying device – Including differential amplifier
Reexamination Certificate
2007-02-20
2009-06-09
Choe, Henry K (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including differential amplifier
C330S257000
Reexamination Certificate
active
07545213
ABSTRACT:
An operational amplifier according to an embodiment of the invention includes: a control signal input terminal receiving a digital control signal from an external device; first and second transistors as a differential pair of a differential amplifier circuit; a constant current circuit supplying a predetermined current to the differential pair; a first resistor provided between the constant current circuit and the first transistor and involving a first potential difference; and a second resistor provided between the constant current circuit and the second transistor and involving a second potential difference, the operational amplifier changing a resistance value ratio between the first resistor and the second resistor in accordance with the control signal input to the control signal input terminal.
REFERENCES:
patent: 4462003 (1984-07-01), Takamatsu
patent: 6445251 (2002-09-01), Robinson
patent: 6734736 (2004-05-01), Gharpurey
patent: 11-88071 (1999-03-01), None
Choe Henry K
McGinn IP Law Group PLLC
NEC Electronics Corporation
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