| 摘要 |
PROBLEM TO BE SOLVED: To provide a light receiving amplifier from which offset to be caused by a difference in voltage between a base and an emitter of an emitter follower of an output part of a trailing amplifier is removed. SOLUTION: The amplifier is constituted of a first preamplifier 1 to convert output current of a photodiode PD into voltage, a second preamplifier 2 with the same structure as the first preamplifier but to receive no input current, the trailing amplifier 4 to perform differential amplification of the output of the first and second preamplifiers 1, 2, an emitter follower Q1 for feedback to negatively feed the output of the trailing amplifier 4 back to the input side of the trailing amplifier 4, and an emitter follower Q2 for output to be connected in parallel with the emitter follower Q1 for feedback and to output output voltage of the trailing amplifier 4. An offset removing circuit 8 to remove the offset due to both of the emitter followers Q1, Q2 by extracting the current equivalent to feedback current of the emitter follower Q1 from the emitter of the emitter follower Q2 for output is provided in the amplifier. |
