| 摘要 |
PURPOSE:To improve the stability and life of a resistor while widening the setting range of a resistance value by measuring the resistance value of a variable resistance element by connecting a fixed resistor in series to the element, and by exercising negatie feedback control over the element by a negative feedback circuit. CONSTITUTION:For the measurement of the source-drain resistance Rx of an FET4, a resistance R1 whose resistance value is known is inserted in series. Then, a current is flowed to a terminal 1 and the source-drain voltage of the FET4 and the terminal voltage of the resistance R1 are applied to differential input amplifiers 12 and 13, whose outputs are inputted to a divider 14. Consequently, the ratio of the resistance Rx to fixed resistance R1 is detected and a voltage corresponding to a desired resistance value is applied from a terminal 4 to make a comparison between the both; and negative feedback is provided to the FET4 according to the comparison result to obtain the desired resistance value. |
