Bandwidth enhancement technique for CMOS RGC transimpedance amplifier

A technique that can increase the bandwidth of a regulated cascode (RGC) transimpedance amplifier (TIA) is presented. The proposed new RGC input topology with a positive amplifier and an inductor enables the control of the input impedance of the circuit and isolates the large input parasitic capacitance. Using this mode the dominant pole of the input node is shifted up to a high frequency, and then the bandwidth of the CMOS RGC TIA is improved. To verify the feasibility of the proposed technique, the CMOS RGC TIA is implemented using a 1P6M 0.18 μm RF CMOS technology. The 3 dB bandwidth of 4.98 GHz is measured in the presence of a 0.5 pF photodiode capacitance with a 1.8 V supply voltage. The measured result shows that the bandwidth of the TIA can increase by about 2 GHz larger than that with the conventional RGC configuration.