| 摘要 |
PURPOSE:To uniformly set the on-resistances of bare FETs at a low value so as to improve the accuracy, by respectively constituting switching means by using P channel MOSFETs connected between a high-reference voltage source and input terminal and N channel MOSFETs connected between a low- reference voltage source and the input terminal. CONSTITUTION:A switching circuit 6-i is composed of a P channel MOSFET T3 connected between the input terminal 2-i of a converting section 1 and a high reference voltage Vrefh and an N channel MOSFET T4 connected between the input terminal 2-i and a low reference voltage Vrefl. Gates of the MOSFETs T3 and T4 are commonly connected with each other and connected with the output terminal of an inverter 3-i and a digital signal Si is supplied to the input terminal of the inverter 3-i. When the digital signal Si is '1', gate potential of the MOSFETs T3 and T4 becomes 0V and the MOSFET T3 is turned on and the other MOSFET T4 is turned off. On the contrary, when the digital signal Si is '0', the gate potential of the MOSFETs T3 and T4 becomes VDD and the MOSFET T4 is turned on and the other MOSFET T3 is turned off. Therefore, both the on-resistances of the MOSFETs T3 and T4 become low values and they almost coincide with each other.
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