Patent ID: 7859810

Claim:
A photocoupler comprising: a light emitting device; a drive circuit connected to a power supply terminal, an input terminal, and a ground terminal, and configured to drive the light emitting device in accordance with a digital signal inputted to the input terminal and cause the light emitting device to output an optical signal; a clamp circuit including a first transistor connected to the input terminal; and a light receiving section configured to convert the optical signal to an electrical signal for output, for an input voltage to the input terminal being within a range between a first voltage and a second voltage, the photocoupler being allowed to enter an operation mode in which the drive circuit, in response to the digital signal inputted thereto, drives the light emitting device to convert the digital signal to the optical signal, and the electrical signal is externally outputted from the light receiving section, and for an input voltage to the input terminal being outside the range between the first voltage and the second voltage, the photocoupler being allowed to enter an inspection mode in which the drive circuit stops driving the light emitting device, the first transistor of the clamp circuit is turned on, and a current generally equal or proportional to a clamp current of the clamp circuit is supplied to the light emitting device so that characteristics of the light emitting device can be measured.