A plurality of transistors in which ratios of a channel length L to a channel width W, α=W/L, are different from each other is provided in parallel as output side transistors 105a to 105c in a current mirror circuit 101 which amplifies a photocurrent of a photoelectric conversion device and an internal resistor is connected to each of the output side transistors 105a to 105c in series. The sum of currents which flow through the plurality of transistors and the internal resistor is output, whereby a transistor with large amount of α can be driven in a linear range with low illuminance, and a transistor with small amount of α can be driven in a linear range with high illuminance, so that applicable illuminance range of the photoelectric conversion device can be widened.