Abstract: A semiconductor device includes a first trans-impedance amplifier, a second trans-impedance amplifier, a peak hold circuit, a comparator and a threshold current setting circuit. The first trans-impedance amplifier converts a first current signal generated by a first photodiode, into which an optical signal is input, into a first voltage signal. The second trans-impedance amplifier converts a second current signal generated by a second photodiode, to which an optical signal is blocked, into a second voltage signal. The peak hold circuit holds the peak value of the first voltage signal. The comparator outputs a pulse on the basis of the first and second voltage signals. The threshold current setting circuit draws out a threshold current.

Abstract: A semiconductor device includes a first trans-impedance amplifier, a second trans-impedance amplifier, a peak hold circuit, a comparator and a threshold current setting circuit. The first trans-impedance amplifier converts a first current signal generated by a first photodiode, into which an optical signal is input, into a first voltage signal. The second trans-impedance amplifier converts a second current signal generated by a second photodiode, to which an optical signal is blocked, into a second voltage signal. The peak hold circuit holds the peak value of the first voltage signal. The comparator outputs a pulse on the basis of the first and second voltage signals. The threshold current setting circuit draws out a threshold current.

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.