A 3-tap digitally programmable transversal filter in 90 nm CMOS for equalization up to 30 Gb/s

This paper describes a fully-differential 3-tap transversal filter in 90 nm CMOS capable of equalizing NRZ data up to 30 Gb/s. A traditional traveling wave filter structure is modified to increase the filter´s bandwidth. Digital programmability is provided for the tap gains, an integrated pre-amplifier, and tuning varactors. The design is 600 μm × 500 μm and draws 25 mA from a 1 V supply. It is the first reported CMOS transversal filter operating above 10 Gb/s.