Design of a 25Gbps Low-Noise and Fast-Response Transimpedance Amplifier for AI Optical Interconnect Receivers

Addressing the stringent demands for high speed, low latency, and signal integrity in optical interconnects for AI data centers, this paper proposes a 25Gbps low-noise transimpedance amplifier (TIA) with a gain-enhancement technique, realized using 0.18[Formula: see text]m SiGe BiCMOS technology. Targeting the characteristics of high-density interconnection within AI clusters, this design effectively extends the bandwidth by employing the inductor peaking technique; the adjustable gain-enhancement technique is utilized to reduce the equivalent input noise, thereby ensuring the accuracy of massive model parameter transmission; a fast response is achieved through adaptive current extraction at the input to accommodate AI low-latency communication. Furthermore, it integrates a DC cancellation technique with feedforward and an Received Signal Strength Indicator (RSSI) circuit. A limiting amplifier incorporating a single-ended-to-differential conversion stage, followed by an output buffer, is cascaded in the back end. Test results show that the main TIA achieves a transimpedance gain of 62.6 dB[Formula: see text] and a -3dB bandwidth of 20.3 GHz; the equivalent input noise current is as low as 9.03 pA/ [Formula: see text] at a 25Gb/s operating rate, and the power consumption is only 63mW under 3.3V/1.8V supply voltages, making it suitable for large-scale parallel AI optical interconnect applications.