| 摘要 |
PROBLEM TO BE SOLVED: To suppress noise by improving an impedance converter in a current-voltage conversion circuit having the impedance converter and an operation amplifier. SOLUTION: An impedance converter 111 includes a gate grounding MOS transistor Q3, and constant current sources I3, I4. The constant current source I3 is connected between the drain of the MOS transistor Q3 and a source (Vdd), and the constant current source I4 is connected between the source of the MOS transistor Q3 and the ground (GND). A current input is supplied to the source of the MOS transistor Q3, and a current output is obtained from the drain of the MOS transistor Q3. A transistor constituting the constant current sources I3, I4 having mutual conductance sufficiently smaller than the MOS transistor Q3 is employed. Because a current mirror circuit is not employed, a large noise current which may otherwise be produced by two transistors is not added, thus resulting in suppressed noise power. COPYRIGHT: (C)2004,JPO
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