| 摘要 |
PROBLEM TO BE SOLVED: To enable the regulation of the gate voltage of an output transistor for improving the accuracy of the output impedance of an open-drain output circuit. SOLUTION: An output transistor control circuit 13 to control an output transistor 14 into a conducting state or into a non-conducting state, a voltage generating circuit 12 for controlling the high level of the gate voltage of the output transistor 14, and a reference voltage generating circuit 11 to supply a reference voltage Vref for the voltage generating circuit 12 are provided. The output of the voltage generating circuit 12 is constituted in such a way as to be directly supplied with voltage from a dedicated pad 15 or an external terminal by a test mode-selecting signal. As for the trimming of the gate voltage, the output impedance of the output transistor 14 is measured to enable the trimming of the gate voltage Vglevel so as to satisfy reference impedance.
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