This work investigates two silicon (Si) photodiodes (PDs) fabricated in 40 nm standard CMOS technology. The basic structure of the proposed Si PD is formed by N+/P-substrate and N-well/P-substrate diodes. The N+/P-substrate PD demonstrates a responsivity of A/W and an electrical bandwidth of 3 GHz for 8 V reverse bias at nm. A 2 Gbit/s µm CMOS Front-End Amplifier for Integrated Differential Photodiodes penetration depth of the photodiode. Its opto-electrical bandwidth is in. laser light impinging on a quadrant photodiode. bandwidth, accuracy, and the penetration depth in the liquid of the bead’s lin-.