为提取弱光检测电路中淹没在噪声中的信号，通常使用高精度放大器尤其是对数放大器来提高电路滤除噪声的能力，其中以对数放大器LOG100为前置放大电路的光电检测电路效果最佳。基于这种电路，提出一种低噪声弱光电检测电路设计方案，以电子元器件相关参数的选择和依据，检测LOG100的输出效果。测量结果表明，输入光信号功率高于1 nW，LOG100噪声滤除性能良好，而低于1 nW时则输出噪声明显增强，可能导致A/D转换输出错误，不利于后续数据处理。 Abstract: In order to extract the signal submerged in the noise in detection circuit， the high-precision amplifiers，especially logarithmic amplifiers， were used to increase the capacity of filtering out the noise，one of the designs was a photoelectric detection circuit using an integrated logarithmic amplifier LOG100 as preamplifier. According to such a circuit，the way of selecting the parameters of the electronic components was raised in designing the low-noise weak-optical detection circuit，and the outputs of LOG100 were detected. Actual measure results show that when the input optical signal power is above 1nW，LOG100 performs a good noise filtering. But when the input optical power is less than 1nW，the noise in output signal is markedly enhanced. Such phenomenon may result in the A/D conversion giving error outputs，and make against to follow-up data processing.