Comparative Study of Different Topologies of Monolithic On-Chip Planar Transformer for Optical VCSEL Driver

Abstract

This article presents a comparative study of different topologies of monolithic on-chip planar transformer, operating at high frequencies and suitable for optical VCSEL driver. The vertical cavity surface emitting laser (VCSEL) driver is presented for optical transceiver systems. At the VCSEL driver output stage, the on-chip transformer is used to compensate for large bandwidth and deliver adequate gain. On-chip transformer equivalent circuit model has been proposed and used for simulation and measurement. The eye pattern results show that the VCSEL driver with an on-chip transformer presents good performance. Different topologies of the on-chip transformer are compared and 0,5 µm CMOS technology measurements are considered in the frequency range from 1 GHz to 10 GHz. Square, hexagonal, octagonal, and circular topologies of on-chip transformer have been compared. The circular topology presents a good performance and high-quality factor. The square shape provides a high inductance value and low quality compared to the other topologies.