A current sensor has a power MOSFET Q1, connected between an electric load
and a power supply, for controlling current that flows through said
electric load, a mirror MOSFET Q2, connected in parallel to said power
MOSFET Q1, in which a portion of the current flowing through said power
MOSFET flows, and a current detection resistor RC connected between a
source electrode of said power MOSFET and a source electrode of said
mirror MOSFET. An inverting amplifier circuit CP of the current sensor 3
inverts and amplifies the voltage signal, which has been converted to
voltage by the current detection resistor RC, and outputs the signal,
thereby converting positive and negative voltages generated across the
current detection resistor RC to a positive voltage.