| 摘要 |
PURPOSE:To stabilize an output for a long period by applying a DC and an AC voltage to a gate insulating film and a photosensitive body, and detecting the AC component of a drain current proportional to the division ratio of the AC impedance of the photosensitive body and a fixed resistance provided between an auxiliary electrode and a DC power source. CONSTITUTION:A blocking film 8 is provided as the auxiliary electrode under a moisture sensitive body 9 and the moisture permeable gate electrode 10 of an FET which has a source area 2 and a drain area 3, and connected to a DC power source VB through the fixed resistance R1. Further, a load resistance RL and a coupling capacitor CO are connected to an electrode conductive film 6 and a resistance R2 and a coupling capacitor CC are connected to an electrode film 10. Further, when electrostatic capacities of the moisture sensitive body 9, and a silicon dioxide film 5 and a silicon nitride film 7 are denoted as Cs and Ci, a voltage Eo outputted to the film 8 is as shown by the equation, so maximum variation in the capacity Cs is led out by nearly equalizing the impedance of the capacity Cs to the resistance R1, and both terminals of the moisture sensitive body 9 are held equal to eliminate the cause of the change with lapse of time. |
