A 4.9-mW 4-Gb/s single-to-differential TIA with current-amplifying regulated cascode

This paper presents the design and analysis of the low voltage regulated cascode trans-impedance amplifier (RGC-TIA). Compared to the conventional RGC-TIA which utilizes Common Source (CS) amplifier as the auxiliary amplifier, this structure can operate at the low supply voltage because of employing the Common-Gate-Common-Source (CG-CS) pair as the auxiliary amplifier. The current combining technique in RGC stage reuses the gain of the auxiliary amplifier for current amplifying, which eliminates the current loss in the CG-CS RGC input stage and then improves the overall TIA gain performance. The proposed low phase error active balun is also adopted to increase the immunity of common-mode noise and relax the following LA design. This TIA draws 3.77 mA from 1.3 V only. With a maximum 4-Gb/s data rate, this work achieves a trans-impedance gain of 61.4 dBΩ and provides differential operation within 10 degrees phase difference.