| 摘要 |
PURPOSE:To compensate a differential signal component derived by the parasitic capacity of the sensor resistance side by using only one stage operational amplifier by dividing the feedback resistance of an operational amplifier that amplifies the output voltage of a sensor element and grounding the dividing point by a trimmer capacitor. CONSTITUTION:The feedback resistance of an operational amplifier (non- inversion amplifier) OPA that amplifies the output voltage of a solid-state image sensor element is divided into R1 and R2 and the dividing point is grounded by trimmer capacitor Ct, and at the same time, the feedback capacity Cd is connected in parallel to R1, R2. An equivalent feedback impedance Zft in the operational amplifier OPA becomes ZFT=R1+R2 when the condition of an expression I holds. In this case, to input a voltage signal of >=2V to an analog multiplexer MPX at sensor resistance Rp=100MOMEGA and the parasitic capacity Cs=about 0.2pF, it is necessary to set to R1+R2=about 20MOMEGA. When set to R1=20MOMEGA, R2=1MOMEGA, Cd=1pF, Ct=22.1pF from the relation of the expression I, A commercial trimmer capacitor Ct of about 20pF can be used.
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