| 摘要 |
PURPOSE:To linearize capacity and period conversion characteristics without any influence of distributed capacity generated in a negative feedback circuit by making a discharging current constant by using a negative resistance circuit which relaxes a current from sensor capacity to the negative feedback circuit. CONSTITUTION:The negative resistance circuit NR is added to the input terminal of a buffer gate G1 to maintain proportional relation. The circuit NR consists of an operational amplifier Q3 and resistances R4-R6. Further, a capacitor C2 is added which determines a bias point automatically while setting the DC gain of the amplifier Q3 to 1. Resistances R4 and R5 are connected between the output terminal of the amplifier Q3 and its uninverted input terminal '+' and inverted input terminal '-' respectively. One terminal of a resistance R6 is connected to the inverted input terminal '-' of the amplifier Q3 and the other terminal is connected to a common potential point COM through the capacitor C2. Discharge characteristics of the waveform of the input voltage to the gate G1 have a linear gradient and the relation between its capacity and period is as shown by an equation, where i0 is the current flowing through the resistance R3, E the voltage, C1 the sensor capacity, and t1 a discharging period.
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