Low-noise amplification of voltage response for thermopile optical detectors

Abstract A technique is presented to amplify the voltage response of thermopile optical detectors. It is based on the parallel combination of multiple operational amplifiers. The background noise of the voltage response has been deceased, which significantly improves the repeatability of the measurement results. Thus, this technique enables the same detector to measure weaker optical power or irradiance at the same precision level. The corresponding amplifying circuit is designed and fabricated. For the same detector, the experimental results show that the standard deviation of the background noise of the combined n op-amps is about 1 / n lower comparing with the conventional single op-amp scheme, which is consistent with the theoretical expectations. Furthermore, the lasers of 10 μW and 1μW were also measured by the specific detector and the amplifier circuit. For a 10 μW response, the measurement repeatability of the 8-combined op-amps is about 1.4%, which is better than the 3.3% of a single op-amp. For 1 μW laser, the measurement result of voltage response of the 8-combined op-amps can be precisely quantified; however, the result of the single op-amp is hardly distinguished. The presented technique based on multiple op-amps is practical and can be potential in many applications. We hope this technique could offer help for expanding the measurement ranges of thermopile optical detectors at weaker optical power and irradiance.