| 摘要 |
PURPOSE:To obtain photodetecting voltage in which a variation component due to temperature change is offset, by providing a precharging circuit and a reference voltage generating circuit which are influenced by temperature change or the like similarly and reducing reference voltage from the reference voltage generating circuit less than constant voltage from the precharging circuit. CONSTITUTION:The precharging circuit 2 consists of MOSFETs Q1, Q2 and the constant voltage VP is VDD-VT obtained by subtracting the threshold voltage VT of the MOSFET Q1 from the power supply voltage VDD. The reference voltage generating circuit 3 consists of MOSFETs Q3, Q4 having the same characteristics as the MOSFET Q1 and a MOSFET Q5 having the same characteristics as the MOSFET Q2 and the reference voltage VRI is -2VT. Both circuits 2, 3 indicate the same inclination in the temperature characteristics and the change of characteristics due to the dispersion of production and input voltages VIN, VRI to a differential amplifier circuit 4 are similarly changed, so that photodetecting voltage VOUT is offset at its variation and stabilized. |
