| 摘要 |
PURPOSE:To simplify the selector circuit by providing a power changeover switch to both ends of the series connecton between a resistance array comprising n-set of resistive elements (resistance R) connected in series and a high resistance element (resistance nR). CONSTITUTION:A common terminal of the 1st single throw switch 4 is connected to a power voltage Vcc and a common terminal of the 2nd single throw switch 5 is connected to ground, then the potential of connecting points P1-P8 is 15/16Vcc-8/16Vcc respectively by the resistance division to the power voltage Vcc. In connecting the common terminal of the 1st single throw switch 4 to ground and the common terminal of the 2nd single throw switch 5 to the power voltage Vcc, the potential at connecting points P1-P8 is 1/16Vcc-8/16Vcc respectively. In selecting the voltage by digital inputs D0-D2 of the selector circuit 6, a reference voltage with 4-bit of resolution is obtained by using the selector of 3-bit switch tree decoder structure.
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