circuit differential pair are generally set to be equal 1 1 however in the current voltage converting circuit of this embodiment the sizes of the nmos transistors mn 1 and mn 2 constructing the differential amplifying circuit differential pair are selected such that the sizes are different from each other for example the sizes are selectively set to 2 1 this is because linearity near the limit electric current between an input voltage vin and an output electric current iout is considered the operation of the current voltage converting circuit 6 of the embodiment will next be explained the constant electric current io is basically distributed to electric currents i1 and i2 provided to the pmos transistors mp 1 and mp 3 in accordance with the input voltage vin and an electric potential difference of the bias voltage vbiasa the electric current i1 provided to the pmos transistor mp 1 becomes the output electric current iout by the current mirror construction formed by the pmos transistors mp 1 and mp 2 and is supplied to the electric current control oscillator 7 here it is important that the input voltage vin and the output electric current iout are linear it will be next explained that the current voltage converting circuit 6 of the embodiment is also attained near the limit electric current in the following explanation for brevity of the explanation the size ratio of the nmos transistors mn 1 and mn 2 is set to 2 1 further the electric potentials of the sources of.