Monolithic transformer and its application in a high-speed optical interconnect VCSEL driver

A novel vertical cavity surface emitting laser (VCSEL) driver is presented for high-speed optical interconnect. At the output stage of the driver, a transformer is used to compensate the bandwidth limitations imposed by transistors, pads and packaging parasitic. At the same time, a monolithic transformer equivalent circuit model applied in the circuit design and simulation of the VCSEL driver is proposed. Using this model, the driver has been designed and fabricated, and measurement results show that the driver with monolithic transformer compensation achieves 25% rise time and 20% fall time reduction compared to the driver without transformer. The eye diagram has been improved considerably.