An amplifier with AGC for the 80 Mbit/s optical receiver of the CMS digital optical link

An 80 Mbit/s amplifier has been developed for the optical receiver of the CMS tracker control link. Four channels of the circuit have been integrated in a 0.25 µm commercial CMOS process using radiation tolerant layout practices to achieve the required radiation tolerance. An Automatic Gain Control (AGC) loop allows for detection of wide dynamic range input signals (10 µA to 500 µA photocurrent) with minimum noise, compatible with the maximum expected radiation-induced drop in quantum efficiency of the PIN photodiode. A second feedback loop compensate a photodiode leakage current up to 100 µA. 1