4-Channel 2.5-Gb/s/ch CMOS Optical Receiver Array for Active Optical HDMI Cables

This paper introduces a 2.5-Gb/s optical receiver implemented in a standard 1P4M 0.18um CMOS technology for the applications of active optical HDMI cables. The optical receiver consists of a differential transimpedance amplifier(TIA), a five-stage differential limiting amplifier(LA), and an output buffer. The TIA exploits the inverter input configuration with a resistive feedback for low noise and power consumption. It is cascaded by an additional differential amplifier and a DC-balanced buffer to facilitate the following LA design. The LA consists of five gain cells, an output buffer, and an offset cancellation circuit. The proposed optical receiver demonstrates transimpedance gain, 1.55 GHz bandwidth even with the large photodiode capacitance of 320 fF, 16 pA/sqrt(Hz) average noise current spectral density within the bandwidth (corresponding to the optical sensitivity of -21.6 dBm for BER), and 40 mW power dissipation from a single 1.8-V supply. Test chips occupy the area of including pads. The optically measured eye-diagrams confirms wide and clear eye-openings for 2.5-Gb/s operations.