Analog integrated lock-in amplifier for optical sensors

Our work that is described here advances a topology for an analog integrated lock-in amplifier (LIA) for optical sensors. We developed a prototype for application in a plastic optical fiber sensor to measure refractive index in an aqueous medium. The design aims at the integration of all system components in silicon and the generation of a low power and low voltage circuit, to allow its use in portable applications. The amplifier topology features differential inputs and outputs to mitigate problems with noise and interference. The prototype trans-impedance amplifier occupies 0.374 mm
²
in a 0.18 μm CMOS process.