A 6 GHz phase-locked loop using AlGaAs/GaAs heterojunction bipolar transistors

Abstract
The authors fabricated in an AlGaAs/GaAs heterojunction bipolar transistor (HBT) process, that can be used as a building block for clock-recovery circuits in high-speed fiber-optic receivers, so that the maximum data rate of fully integrated receivers can be extended from 2.5 Gb/s to 6 Gb/s. A block diagram of the PLL circuit is shown and a micrograph of the chip is presented.