| 摘要 |
PROBLEM TO BE SOLVED: To provide an interface circuit having a high breakdown strength at a low cost. SOLUTION: The interface circuit 1 comprises a section 5 for transmitting an input signal to the next stage while insulating electrically, and a section 6 comprising components of high breakdown strength and applying a voltage not higher than a specified level to the input signal transmitting section 5. The input signal transmitting section 5 comprises a photocoupler PC and the constant voltage applying section 6 connected with the connector terminal of a phototransistor PT in the photocoupler PC comprises a first transistor Q1 for high breakdown strength, and a constant voltage diode ZD connected in parallel with the output side of the phototransistor PT.
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