| 摘要 |
PURPOSE:To realize change over or control a test facilitating circuit without using an external control signal by comprising a control circuit which outputs a high level control signal during the normal operation or a low level signal when a power source voltage is raised. CONSTITUTION:A gate is composed of an E type driver MOS transistor 11 connected to the power source VDD and an E type loaded MOS transistor 12 connected between the drain of such transistor 11 and power source VDD, and the drain of transistor 11 is used as the output node 13. A threshold voltage VT of transistor 11 is higher than the power source voltage during normal operation but is lower than that in the test mode or initializing mode, and a threshold voltage of loaded MOS transistor 12 is set to a value equal to that in ordinary operation. Since the transistor 11 is not conductive in the ordinary operation and therefore the node 13 becomes ''1'', and when VDD>VT in the test or initializing mode, the transistor 11 becomes conductive and the node 13 becomes ''0''. |
