| 摘要 |
PURPOSE: To reduce threshold voltage mismatches and low-frequency noises of current mirrors so as to increase the S/N of the current mirrors by providing a means which alternately activates first and second cascode type current mirrors and generates a current mirroring an input current to a common output. CONSTITUTION: In order to allow an output current IOUT to accurately mirror an input current IIN, transistors 310 and 330 must have the same threshold voltage drop (namely, VT). Repetitive cycles for connecting and disconnecting transistors 320 and 340 to and from the transistors 310 and 330 by opening and closing switches 335 and 345 alternately chop the transistors 320 and 340. When the transistors 320 and 340 are alternately chopped, the transistor (for example, transistor 320) having a mismatching threshold voltageΔVT is alternately switched at such a frequency that the mean output current at an output node 350 accurately indicates the input current at an input node 360.
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