| 摘要 |
<P>PROBLEM TO BE SOLVED: To establish compatibility between high-sensitivity optical intensity input detection and large maximum input optical intensity in an optical apparatus provided with a light-receiving intensity monitoring device. <P>SOLUTION: A current detection resistor 202 is connected in series with a light-receiving element 114, and a voltage difference Vdrop generated between both ends of the current detection resistor 202 is detected by a difference amplifier 266. The difference amplifier 266 compares a reference signal Vref with the voltage difference Vdrop, and if they match, the amplifier 266 executes current supply to the light-receiving element 114 even for a path through a transistor 262 not via the current detection resistor 202. The difference amplifier 266 and the transistor 262 cooperate in operating a current limitation function. In this way, even when a resistance value of the current detection resistor 202 is made large to operate the current detection function at high sensitivity, a voltage difference to be generated on both the ends of the current detection resistor 202 when the optical intensity becomes high can be maintained at a constant value, and thus, the compatibility can be established between the high-sensitivity optical input intensity detection and the large maximum input optical strength. <P>COPYRIGHT: (C)2007,JPO&INPIT |
