perform offset correction without considering the on resistances of the switches 47 and 48 thereby eliminating the need to increase the transistor size to reduce the resistances of the switches 47 and 48 a laser power control circuit according to an eighth embodiment of the present invention will be described in the above sixth embodiment since the amplification level g in the first term of the formula 5 expressing the offset voltage is approximately 1000 the first term is neglected from the formula for correcting the offset voltage since vm u2212 vr and vofs 2 are several tens mv at most in the first term of the formula 5 values that are obtained by dividing these values with the amplification level g are sufficiently negligible on the other hand voofsn is a difference voltage between the output voltage of the laser power control circuit 100 which is outputted from the output terminal 23 and the reference voltage vr and this difference voltage reaches several v in the circuit structure as shown in fig6 the base voltage of the semiconductor laser driving transistor 5 is a voltage lower than the voltage value of the positive supply terminal 1 by about 0 7v when the voltage value of the positive supply terminal 1 is 3 3v which is a common value that is supplied to the semiconductor integrated circuit and the reference voltage vr is 100 mv voofsn 3 3 u2212 0 7 u2212 0 1 2 5 v when this voltage is divided by the amplification level g 1000 2 5 mv is obtained which corresponds to 2 5 of the reference voltage vr while it is desirable that the accuracy of the power control should fall within 5 2 5 is not exactly a.