AN ALGAAS INGAAS PSEUDOMORPHIC HEMT MODULATOR DRIVER IC WITH LOW-POWER DISSIPATION FOR 10-GB/S OPTICAL-TRANSMISSION SYSTEMS/

An optical modulator driver integated circuit (IC) has been developed for 10-Gb/s optical communication systems. To achieve both high-freque ncy (HF) operation and low power dissipation, 0.2-mu m T-shaped gate A lGaAs/InGaAs pseudomorphic high electron-mobility transistors (HEMT's) have been employed for their large transconductance g(m) of 610 mS/mm and high cutoff frequency f(T) of 67.5 GHz. In addition, optimizing i nput logic swing, switching transistor size in the output driver, and using cascode-current mirror circuits with small output conductance en able power dissipation as low as 1 W to be achieved at a 10-Gb/s nonre turn-to-zero (NRZ) signal output with 3 Vp-p. This is the lowest value ever reported for power dissipation. As an additional function, the o utput voltage swing can be controlled in the range from 2 to 3.3 Vp-p by the current mirror circuit for the purpose of adjusting the optical -output-signal duty factor through an optical modulator.