Current detection circuit

The present invention provides a current detection circuit. Using a electrostatic capacitor (12) and a diode (13), a gate voltage of a protecting MOSFET (7) is increased when a drain voltage of a power transistor (2) increases. A voltage clamp circuit (14) clamps the maximum voltage of the gate voltage of the protecting MOSFET (7)to a predetermined clamp voltage (Vc). A voltage control circuit (17) controls a drain voltage of a sense transistor (6) so as to substantially coincide with a source voltage of the protecting MOSFET (7). A detection circuit (40) detects the current of the drain of the sense transistor (6). Therefore, even if the substrate bias effect occurs in the protecting MOSFET of the current detection circuit of the power transistor, the current of a load is detected precisely by means of a high voltage negatively fed back by the operation amplifier on the basis of satisfying the resistant voltage between the source and gate of the protecting MOSFET.