| 摘要 |
PURPOSE:To output a stable analog current with simple constitution without the need of any constant voltage power supply by setting the constant current value of a constant current element of an individual conversion circuit receiving a digital signal from a 2nd digit to twice of the constant current value of the constant current element of the individual conversion circuit receiving a digital signal of the preceding digit and connecting series circuit comprising a switch and a constant current element in the individual conversion circuit in parallel so as to impress a voltage. CONSTITUTION:The constant current element 81 of the 1st individual conversion circuit 1 is set to a constant current value having a resolution when a digital signal is converted into an analog signal and the constant current value of the 2nd-n-th constant current elements 82-8n of the 2nd-nth individual conversion circuits is set to twice the constant current value of the 1st-(n-1)th constant current elements 81-8(n-1) of the 1st (n-1)th individual conversion circuits 1-(n-1). Moreover, the series circuits each comprising the photodetector (71-7n) and the constant current element (81-8n) of the 1st-nth individual conversion circuits 1-n are connected in parallel, power is supplied from a power terminal V2 and an analog signal is outputted to an output terminal. Thus, a stable analog current is outputted without constant voltage power supply.
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