| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a current-voltage conversion circuit which prevents the saturation of an operational amplifier at the time of receiving the light of high power, and which can set a limit arbitrarily. <P>SOLUTION: In this circuit, the light is incident on a photodiode 2. When a photocurrent I is generated, a current of mirror ratio as many current decided by resistors 4, 5 through a current mirror circuit 9 is inputted to the operational amplifier 1. In this case, a voltage drop occurs according to the photocurrent I in the resistor 4, but a limiting function will not work if this value is a voltage in which a transistor 8 for limit begins to operation, such as, for example, 0.7 V or lower. However, when the photocurrent I becomes large and the voltage drop in the resistor 4 reaches the voltage in which the transistor 8 begins to operate, the photocurrent I generated in the photodiode 2 is passed to a GND. Consequently, the input current to the amplifier 1 is limited. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
