| 摘要 |
PROBLEM TO BE SOLVED: To reduce low frequency noise (1/f noise) in an operational amplifier. SOLUTION: The differential transistor 110 of a FET constructing an input terminal of a differential amplifier circuit is made to operate outside a stable operation area (=non-saturation area and area which is in the vicinity of saturation area boundary, where Id changes with Vds and which is not usually used). Thus, Id is made to limitedly operate in a range where gm functions, heat generation due to the loss being the product of Vds and Id is suppressed, and a fluctuation due to the heat generation is eliminated to suppress low frequency noise. A level shift circuit 200 consisting of a reference generating part 220 for generating a reference voltage with the potential of the low potential side terminal of the differential transistor as reference potential and a voltage shift part 210 made to operate by the reference voltage and for performing voltage drop is inserted as a means for operating the differential transistor outside the stable operation area, and Vds applied to the differential transistor is thereby determined.
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