| 摘要 |
PURPOSE:To improve the linearity of conversion of a light signal in relation to an input signal by providing a linearity error of an emission efficiency characteristic of a light-emitting means and a linearity error in a reverse characteristic thereto and by making them offset each other. CONSTITUTION:An amplified output S1 obtained by amplifying an input voltage signal VIN of a preamplifier 9 with a gain A and an offset output SO become the base power of N-P-N transistors 10 and 11 forming a differential couple, respectively. In this way, a voltage-current conversion characteristic of a voltage-current converting means has a linearity error in a reverse characteristic to the linearity error of an emission efficiency characteristic of a light-emitting means 4 in a prescribed current range of a current signal. Therefore the linearity errors of the two characteristics offset each other and the linearity error of the conversion rate of a light signal in relation to the input voltage signal diminishes. Thereby the linearity of the conversion characteristic from the input voltage signal to the light signal is improved. |
