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

Abstract

New steady-state fluorometric systems are based on solid state-optoelectronic components such as blue light-emitting diodes, avalanche photodiodes, and standard photodiodes. In the latter case, the noise performance of the front-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 processes the signal from photodetectors without internal amplification is presented. 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/√Hz has been obtained at a shaping time of 200 μs. The circuit exhibits excellent rejection to continuous ambient light and partially suppresses the alternating components. © 1999 American Institute of Physics.