A semiconductor device including: a filter circuit to subdivide and output the received signal as a first signal with a relatively low frequency and a second signal with a relatively high frequency; a first channel containing a photocoupler to convey the first signal output from the filter circuit; a second channel containing an isolator to convey the second signal from the filter circuit; and a signal synthesis circuit to sum and output the first signal conveyed by way of a first channel and a second signal conveyed by way of a second channel.