A 1.25 Gbps DC-coupled laser diode driver with VBE compensation technique

A 1.25 Gbps integrated laser diode driver (LDD) driving an edge-emitting laser has been designed and fabricated in 0.35 μm BiCMOS technology. The IC can provide independent bias current (5–100 mA) with automatic power control, and modulation current (4–85 mA) with temperature compensation adjustments to minimize the variation in extinction ratio. This paper proposed an unique modulation output driver configuration which is capable of DC-coupling a laser to the driver at +3.3 V supply voltage; and combined a VBE compensation circuit, the IC can operate at a wide temperature range (−40 to 85 °C) for date rates up to 1.25 Gbps. VBE compensation technique is used to compensate for variation in VBE over the operating temperature range so as to minimize the variations in rise and fall time of modulation output over temperatures.