A Large Swing, 40-Gb/s SiGe BiCMOS Driver With Adjustable Pre-Emphasis for Data Transmission Over 75 $\Omega$ Coaxial Cable

A fully differential 40-Gb/s cable driver with adjustable pre-emphasis is presented. The circuit is fabricated in a production 0.18 mum SiGe BiCMOS technology. A distributed limiting architecture is used for the driver employing high-speed HBTs in the lower voltage predriver, and a high-breakdown MOS-HV-HBT cascode, consisting of a 0.18 mum n-channel MOSFET and a high-voltage HBT (HV-HBT), for the high voltage output stages. The circuit delivers up to 3.6 V peak-to-peak per side into a 75 Omega load with variable pre-emphasis ranging from 0 to 400%. S-parameter measurements show 42 dB differential small-signal gain, a 3-dB bandwidth of 22 GHz, gain peaking control up to 25 dB at 20 GHz and input and output reflection coefficients better than -10 dB up to 40 GHz. Additional features of the driver include output amplitude control (from 1 V_pp to 3.6 V_pp per side), pulse-width control (35% to 65%) and an adjustable input dc level (1.1 V to 1.8 V) allowing the circuit to interface with a SiGe BiCMOS or MOS-CML SERDES. The transmitter is able to generate an eye opening at 38 Gb/s after 10 m of Belden 1694 A coaxial cable which introduces 22 dB of loss at 19 GHz. Measurement results also demonstrate that the transmitter IC operates as a standalone equalizer for 10-Gb/s data transmission over 40 m of Belden cable without the need for receiver equalization.