Abstract:
A light-emitting unit outputs an optical signal corresponding to an input electric signal. A light-receiving unit is electrically insulated from the light-emitting unit and outputs an electric signal according to the received optical signal as an output signal. In the light-receiving unit, a first light-receiving device outputs an optical current according to the optical signal. A second light-receiving device is provided not to receive the optical signal. A current duplication circuit duplicates a current flowing through the second light-receiving device. A current-voltage conversion circuit converts a current, which is generated by subtracting the current duplicated by the current duplication circuit from a current flowing through the first light-receiving device, into a voltage signal. A comparator output a result of a comparison between the voltage signal converted by the current-voltage conversion circuit and a threshold voltage as the output signal.
Abstract:
A light-emitting unit outputs an optical signal corresponding to an input electric signal. A light-receiving unit is electrically insulated from the light-emitting unit and outputs an electric signal according to the received optical signal as an output signal. In the light-receiving unit, a first light-receiving device outputs an optical current according to the optical signal. A second light-receiving device is provided not to receive the optical signal. A current duplication circuit duplicates a current flowing through the second light-receiving device. A current-voltage conversion circuit converts a current, which is generated by subtracting the current duplicated by the current duplication circuit from a current flowing through the first light-receiving device, into a voltage signal. A comparator output a result of a comparison between the voltage signal converted by the current-voltage conversion circuit and a threshold voltage as the output signal.
Abstract:
A semiconductor device that includes: a first trans-impedance amplifier that converts a first current signal generated by a first photodiode, into which an optical signal is input, into a first voltage signal; a second trans-impedance amplifier that converts a second current signal generated by a second photodiode, to which an optical signal is blocked, into a second voltage signal; a peak hold circuit that holds the peak value of the first voltage signal; a comparator that outputs a pulse on the basis of the first and second voltage signals; and a threshold current setting circuit that draws out a threshold current, which is proportional to a reference current generated on the basis of a voltage difference between a peak voltage output by the peak hold circuit and a reference voltage at the output node of the second photodiode, from the connection between the second photodiode and the second trans-impedance amplifier.