| 摘要 |
PROBLEM TO BE SOLVED: To provide a signal processing circuit which is able to select a high bias current and the satisfactory noise performance or a low bias current and unsatisfactory noise performance. SOLUTION: This signal processing circuit includes an input device 12, which has a high impedance and the low noise characteristic, a first current source 18 which supplies a current of the lowest level to the device 12, additional current source means 26 and 34 which supply additional currents to the device 12 to improve the noise resistance of the circuit, and a switching means 28 which connects the means 26 and 34 to the circuit, when improvement of the noise performance is requested and then disconnects the means 26 and 34 from the circuit to save the power, when no improvement in the noise performance is requested.
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