Low-noise front-end electronics for solid-state fluorometers

New steady-state fluorometric systems are based on solid state-optoelectron ic components such as blue light-emitting diodes, avalanche photodiodes, an d standard photodiodes. In the latter case, the noise performance of the fr ont-end electronics limits the sensitivity of the instrumentation. However, signal detection performed by standard photodiode is appealing in low-cost applications. In this article, a low-noise electronic setup which processe s the signal from photodetectors without internal amplification is presente d. Low-noise preamplification and optimal signals shaping allow to minimize the fluorometric measurement uncertainty. The circuit has been accordingly developed and tested in operation. Using a low-cost silicon photodiode, a minimum equivalent noise power less than 1 pW/root Hz has been obtained at a shaping time of 200 mu s. The circuit exhibits excellent rejection to con tinuous ambient light and partially suppresses the alternating components. (C) 1999 American Institute of Physics. [S0034-6748(99)01809-2].