| 摘要 |
PROBLEM TO BE SOLVED: To process signals stably at high rate by a constitution, wherein a light-receiving means having a plurality of light-receiving regions and a differential amplifier type current/voltage conversion means for processing the output from the light-receiving means are provided on a same chip. SOLUTION: A main light-receiving region 21 for receiving the reflected light of a main spot comprises four light-receiving elements 21a-21d, e.g. photodiodes, and a side light-receiving region 22 for processing a side spot comprises similar light-receiving elements 22a, 22b. Output currents from the elements 21a-21d are converted into voltages through I-V conversion circuits 31, 32 receiving a first reference voltage. Differential amplification is performed using a second reference voltage, generated from a second reference voltage- generating circuit 50 having same structure as the circuits 31, 32, under a state of no-input. Consequently, DC component is prevented from fluctuating in additive amplification, and the signal is stabilized. The circuits 31, 32, 50 are differential amplifiers having an emitter grounded differential stage, comprising only an NPN transistor and a resistor and since it can perform high rate processings, the entire integrated circuit can be simplified. |
