| 摘要 |
PURPOSE:To facilitate the setting of current ratio and to improve the setting accuracy and conversion accuracy by setting a current ratio by a resistance ratio only at a resistance ladder and using an integration means so as to integrate an output in response to an input digital signal and extracting the result as an analog signal in response to the input digital signal. CONSTITUTION:In using counters 2, 4 of a digital signal Di so as to throw a switch 46 to the position of contacts o, p and to throw a switch 48 to the position of contacts q, r, then a current of low-order bit flows to the switch 46 and a high-order bit current flows to the switch 48, and the voltage generated by a current by the resistance ratio set in the resistance ladder 50 by the switching of the both switches is fed to an integration circuit 36. Then the input fed to an inverting input of an operational amplifier 37 based on the digital signal Di is integrated by the integration circuit 36 and extracted from an output terminal 44 as an analog signal Ao. Thus, the current ratio setting by the area ratio of transistors and number of provision is not required and the setting accuracy and conversion accuracy are improved.
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