A bandwidth enhancement technique for CMOS TIAs driven by large photodiodes

A new method of enhancing the bandwidth of a conventional series-peaked transimpedance amplifier (TIA) driven by a large photodiode is introduced. It is shown that by using N identical TIAs in parallel the circuit bandwidth can be significantly improved. The advantage of the proposed technique is in its ability to provide large bandwidth enhancements in multi-GHz frequency ranges even when photodiode capacitance is large, without a noticeable increase in TIA core circuit area. This technique is supported by a design example simulated in a 0.13μm standard CMOS technology. Simulation results show a 3dB bandwidth of 26GHz with 0.5pF photodiode capacitance, a transimpedance gain of 51dBΩ and group delay of 33.5±4ps. The proposed technique shows an overall bandwidth enhancement ratio of 3.25 with less than 0.1dB gain ripple resulting in higher bandwidth enhancement than previously reported for large photodiode capacitances.