A 1-pJ/bit 80-Gb/s 2¹⁵-1 PRBS Generator With a Modified Cherry-Hooper Output Driver

An 80-Gb/s 2¹⁵-1 pseudorandom binary sequence (PRBS) generator suitable for testing binary communication systems is presented. Implemented in a 130-nm SiGe process, the circuit is optimized for low power dissipation. For the core functionality, an energy efficiency of 1 pJ/bit is achieved, which is one of the best values among comparable published designs. In addition, the improvement of the output signal in time domain and frequency domain is targeted. The key factors affecting an ideal PRBS spectrum are identified and addressed from the system and circuit point of view. This results in spur suppression of higher than 40 dB, which is 15 dB better than previously reported works exceeding 40 Gb/s. As an output driver, a modified Cherry-Hooper amplifier is chosen. A parametrized design methodology for obtaining Bessel response is introduced and the amplifier is optimized for low power operation. Measurement results show a single-ended output signal with over 300-mV eye opening, 0.6-ps rms jitter, and a signal-to-noise ratio better than 10.5 at 80 Gb/s, which is the best-in-class output eye diagram for a PRBS generator, to the best of our knowledge.