Gigabit CMOS transimpedance amplifiers for optical communication applications

A number of gigabit transimpedance amplifiers are realized in submicron CMOS technologies. By exploiting regulated cascode (RGC) configuration for the input stage, the amplifiers efficiently isolate the large input parasitic capacitance and hence achieve significant bandwidth improvement. A 1.25-Gb/s RGC TIA demonstrates 950 MHz bandwidth for O.5 pF photodiode capacitance and the only 93 MHz difference even for 1 pF photodiode capacitance. Also, a 2.5-Gb/s RGC TIA realized in a 0.6 /spl mu/m CMOS technology demonstrates 2.2 GHz bandwidth for O.5 pF photodiode capacitance, confirming the RGC mechanism. In addition, a differential RGC TIA is realized in a 0.25 /spl mu/m CMOS technology. Optical measurements clearly show 1.25-Gb/s operation for 1 pF photodiode capacitance with 80 dB/spl Omega/ transimpedance gain.