A 2.85 pJ/bit, 52-Gbps NRZ VCSEL Driver with Two-Tap Feedforward Equalization

─We report an energy-efficient vertical cavity surface-emitting laser (VCSEL) driver implemented in a 130 nm SiGe HBT technology. Operation at data rates as high as 60 Gbps is demonstrated with the use of two-tap feed-forward equalizer (FFE) using a differentiator circuit at the output driver stage that eliminates the need for inductors and results in compact area (0.032 mm
²
). The current contribution of the differentiator produces a trade-off between energy efficiency and bandwidth enhancement. Error-free (BER < 10
⁻¹²
) non-return-to-zero (NRZ) transmission up to 52 Gbps is reported at an efficiency of 2.85 pJ/bit.