| 摘要 |
PROBLEM TO BE SOLVED: To correct the amount of change in a drain current because of deterioration and a temperature change even if the deterioration and temperature change occur in a photo transistor. SOLUTION: A photodetector 1 includes: a light shielding phototransistor T0; the phototransistor T1; a buffer amplifier Buf; a constant current source 2; and a current-voltage converter 3, and the like. A fixed voltage is applied to the gates of the light shielding phototransistor T0 and the photodiode T1 by a first constant voltage source 4. The source voltage of the light shielding phototransistor T0 is identical to that of the phototransistor T1 by the imaginary short circuit of an operational amplifier Amp. A fixed drain current flows to the light shielding phototransistor T0 by the constant current source 2, and the drain voltage of the light shielding phototransistor T0 is floated. The gate voltage of the light shielding phototransistor T0 becomes equal to that of the phototransistor T1 by the buffer amplifier Buf. COPYRIGHT: (C)2009,JPO&INPIT |
