| 摘要 |
PURPOSE:To eliminate the influences due to the levels and temperatures of the high voltage to be applied, the manufacturing conditions, etc., by detecting the source-drain current of a field effect transistor while the high voltage is applied and the threshold level voltage is varying and discontinuing the application of the high voltage when the detected current reaches a prescribed level. CONSTITUTION:A source-drain current is detected by a drain voltage application/current detection circuit 4 and then compared with a reference current IR generated by a reference current generating circuit 6. When the former current exceeds the level of the latter current, a control signal CS is set at high voltage generation stop level so that the generation of the high voltage is discontinued by a high voltage generating circuit 2. Thus the high voltage so far applied to a field effect transistor FT1 is eliminated. Then the change of the threshold level voltage is stopped. As a result, the control accuracy is improved for the threshold level voltage of the transistor FT1. |
