| 摘要 |
PROBLEM TO BE SOLVED: To improve the measurement accuracy of toner concentration. SOLUTION: An amplifier processing the signal of an infrared photodetector 2 is constituted of a first amplifier OP1 and a second amplifier OP2; and in the first amplifier OP1 the input terminal of a reference voltage Vref1 and the cathode terminal of the infrared photodetector 2 are connected to a positive input terminal, and the anode terminal of the infrared photodetector 2 is connected to a negative terminal and also is connected to an output side through a sensitivity adjustment volume VR1. In the second amplifier OP2, the input terminal of the reference voltage Vref1 is connected to the positive input terminal, and the output of the first amplifier OP1 is connected to the negative terminal through a first resistor R2 and also is connected to the output side through a second resistor R3. Further, the first amplifier OP1 is formed by the operational amplifier of a CMOS, and the second amplifier OP2 is formed by a bipolar operational amplifier. |
