Abstract: A blood alcohol detection method was investigated based on NIR(near-infrared) spectroscopy.And a lownoise, low-drift and high-precision preamplifier was designed to detect the blood alcohol volume fraction accurately. In the current-voltage conversion section, the simulation of drift and error of two kinds of circuits were carried out by Multisim software.AD620 was selected in the preamplifier part which could improve the CMRR(common mode rejection ratio) of circuits. The results of simulation showed that the current-voltage conversion circuit of symmetrical compensational low-temperature drift can suppressed the drift and reduced error better. Compared with the OP07 current-voltage conversion circuit, the error could be reduced by 2％, while the draft could be reduced by 97％, which could support weak signal analyzing.

Key words: near-infrared, pre-amplifier circuit, low drift, high-precision, alcohol volume fraction