A configurable fluorescence sensing front-end for ultra-low power and high sensitivity applications

This paper presents an ultra-low power, high sensitivity configurable CMOS fluorescence sensing front-end for implantable biosensors at single-cell level measurements. The front-end is configurable by a set of switches and consists of three integrated photodiodes (PD), three transimpedance amplifiers (TIA) for detecting a current range between 1 pA up to 10 mA. Also, an ambient light canceling technique is proposed to make the sensor operate under different environmental conditions. The proposed front-end could be configured for ultra-low light detection or ultra-low power consumption. The circuit is designed and fabricated in a 0.35 µm standard CMOS technology, and the measurement results are presented. The minimum integrated input-referred current noise is measured as 1.07 pA with the total average power consumption of 61.8 µW at an excitation frequency of 80 Hz. For ultra-low-power configuration, the front-end has an average power consumption of 119 nW and input integrated current noise of 210 pA at an excitation frequency of 20 kHz.