This work presents an Analogue Front-End (AFE) interface for biophotonics data capture, featuring a Silicon Photomultiplier (SiPM) as the primary sensing component. The SiPM is uniquely suited for high-sensitivity, in-vivo cancer tumour detection biophotonics applications due to its high dynamic range, enabling detection of optical power levels as low as 1 pW. This capability is critical for applications such as Autofluorescence (AF) spectroscopy, where the light emission from endogenous fluorophores are inherently weak. The SiPM’s performance requires AFE designs with ultra-low noise floors, wide dynamic range, and bandwidths spanning 1 kHz to tens of kHz to resolve real-time light-tissue interactions. To meet these requirements, a single-ended Continuous Time (CT) second-order ∆Σ modulator was developed, featuring a hybrid Cascade of Integrators with Feed-Forward and Feedback (CIFF-B) loop-filter topology and a tri-level current Digital to Analogue Converter (DAC) to suppress in-band noise. To further enhance the dynamic range of the AFE, a programmable-gain Flipped Voltage Follower (FVF) current buffer was added, enabling direct digitisation for optical inputs ranging from pW to µW. In addition to extending the signal range, the FVF ensures stable biasing and facilitates direct interfacing with the photodetector, simplifying system integration. Two custom ICs were fabricated in 180 nm CMOS: one consisting solely of the ∆Σ modulator, and the other integrating the FVF stage. The latter occupies an active area of 0.23 mm2 and consumes a power of 2.17 mW from a 1.8 V supply. Electrical and optical validation has demonstrated a 114.5 dB current sensing dynamic range and a resolution of 4.8 nA in a 30 kHz bandwidth, equivalent to pW-level optical detection. The results position this AFE as a high-precision, energy-efficient solution for biophotonics systems, enabling a miniaturised, multi-modal sensing interface suitable for in-vivo cancer tumour detection.

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