The ONET4211LD is a laser driver for multiple fiber optic applications up to 4.25 Gbps. The device accepts CML input data and provides bias and modulation currents for driving a laser diode. Also provided are automatic power control (APC), temperature compensation of modulation current, fault detection, and current monitor features. The device is available in a small-footprint, 4 mm × 4 mm 24-pin QFN package. The circuit requires a single 3.3-V supply. This power-efficient laser driver is characterized for operation from -40°C to 85°C.