PURPOSE: To adjust an inverting voltage even after the circuit is formed on a semiconductor chip by excluding a limit condition such as dependency of a power supply voltage and a process.

CONSTITUTION: This circuit consists of a PROM cell 4 receiving a voltage input 1 as its gate input and receiving a high voltage power supply 3 at its source, an N-channel semiconductor 5 whose gate and drain connect to a connecting point 8 of a drain of the cell 4 and whose source connects to ground, and an inverting logic element 7 whose connecting point 8 is used for an input point and whose output is obtained at an output point 2. When the cell 4 is written, the threshold level of the cell 4 gets higher. A high voltage is detected by utilizing the operation that the cell 4 is not conductive when the input voltage of the input 1 does not reach the threshold level of the cell 4 or over. The threshold level is further increased through additional write to increase the inverting voltage or the cell 4 is erased to reset the inverting voltage thereby excluding the limit condition.