| 摘要 |
<P>PROBLEM TO BE SOLVED: To eliminate a change of a temperature characteristic in sensitivity of a photodiode PD due to a change in a wavelength in a light receiving amplifier circuit where a signal from the photodiode PD on which there are incident optical signals with plural types of wavelengths such as 780 nm of a CD-R/RW disk and 650 nm of a DVD±R/RW disk. <P>SOLUTION: A differential amplifier A3 having input resistors Rs31 and Rs32 making the temperature characteristic of sensitivity of PD to be zero at the time of the wavelength of 650 nm, an input voltage dividing resistor Rf31 and a feedback resistor Rf32, and a differential amplifier A4 having input resistors Rs41 and Rs42 making the temperature characteristic to zero at the time of the wavelength of 780 nm, an input voltage dividing resistor Rf41 and a feedback resistor Rf42 are arranged. Output from either amplifier is used in accordance with the two wavelengths. Even if the temperature characteristic of sensitivity of PD changes due to the change of the wavelength, it is canceled by the temperature characteristic of the light receiving amplifier circuit, and the temperature characteristic as the whole optical pickup element 21 can be made zero. <P>COPYRIGHT: (C)2004,JPO&NCIPI |
