Analysis and Design of Inductorless Transimpedance Amplifier Employing Nested Feedforward Noise-Canceling Amplifiers

In this article, we propose a nested feedforward noise canceling (NFF-NC) technique for transimpedance amplifier (TIA) in optical link communication. The proposed technique minimizes the noise voltages due to both the first and second stages of the TIA, which provides substantial improvement in its noise performance over conventional noise canceling (NC) topology. Comprehensive analysis and comparison are performed between two techniques. While not degrading other key performance parameters (e.g., bandwidth, gain, and power consumption), our proposed scheme presents 30% noise reduction compared to conventional scheme. The proposed NC architecture provides the improved stability since NFF-NC scheme inherently presents an additional left half-plane (LHP) zero due to the FF-stage. The loop stability performance is verified over several process corners, temperatures, and voltage variations confirming the detailed analysis in its loop gain and loop parameters. The proposed NFF-NC TIA was implemented in a 65-nm CMOS technology. The implemented TIA consumes 10.1 mW of power from a 1.3-V supply and occupies 0.037 mm 2 of core area. The measurement results show that the proposed TIA presents dc transimpedance gain of 56.3 dB \Omega and bandwidth (−3 dB) of 6.5 GHz. An average input-referred noise current density, \overline {i_{n,\text {in},\text {avg}}} , is 15.1 pA/(Hz) 1/2 over the bandwidth. Eye diagram is also measured with a pseudorandom binary sequence (PRBS) of 2 7 - 1 with the data rate at 8.5 Gb/s.