a voltage detection unit generates a detection voltage signal representative of a potential difference caused by a current to be detected . a reference current generation unit generates a first reference current and a second reference current having a linear relationship therebetween . in response to the detection voltage signal and the first reference current , a transfer unit determines a first operation voltage . furthermore , the transfer unit determines a second operation voltage and a transfer current in response to the first operation voltage and the second reference current . the second operation voltage is substantially equal to the first operation voltage . a detection current signal having a linear relationship with the current to be detected is generated through subtracting at least the second reference current from the transfer current .