A 10Gb/s 6Vpp differential modulator driver in 0.18μm SiGe-BiCMOS

This paper describes a 10Gb/s, digitally-controlled distributed amplifier (DA) implemented in 0.18μm SiGe (60GHz peak-fT) with 6Vpp differential output swing, <;20ps symmetric rise/fall times, negligible additive jitter and >10dB return loss across 30GHz bandwidth; performance suitable for driving a dual (i.e., balanced) MZ modulator. Unlike conventional DAs, which use a passive transmission line at the input to feed each amplifier cell with the correct signal phase, the gain cells in the prototype modulator driver are driven by digital latches. The fully-digital interface at the DA input leads to a scalable design by eliminating the performance impairments of the input transmission line.