Patent ID: 8009709

Claim:
A DC-coupled driver for driving a vertical cavity surface emitting laser (VCSEL) diode comprising: a first positive voltage supply for providing a supply voltage to the driver during operation; a ground rail for providing a current return path to the first positive voltage supply; a differential input stage for receiving data and complementary data signals from a signal source, the differential input stage comprising a first and a second transistor, a first and a second output terminal, each connected to the first and a second transistor, respectively, and a modulation current source for biasing the first and second transistors; a termination resistor having a first and a second terminal; a first current source connected to the first terminal on the termination resistor for providing a current bias to at least one of the VCSEL diode and the first transistor of the differential input stage; a low frequency differential input feedback amplifier for sensing a voltage drop across the termination resistor, and operational to maintain a predetermined voltage drop across the termination resistor; wherein the VCSEL diode is connected directly to the termination resistor for actively controlling a driving voltage on the VCSEL diode; a shunt feedback transimpedance amplifier comprising a bias diode for providing a bias voltage offset, a third transistor for providing gain, and a feedback resistor; a second current source connected to the second terminal on the termination resistor for providing a current bias to the second transistor of the differential input stage; and an inverting voltage to current converter having an output terminal that is coupled to an input of the shunt feedback transimpedance amplifier; wherein the low frequency feedback amplifier further comprises: a first operational amplifier having an inverting input terminal, a non-inverting input terminal, and an output that is connected to an input of the inverting voltage to current converter; a bypass capacitor connecting the non-inverting input terminal to the ground rail; a first input resistor connecting the non-inverting input terminal to the first terminal on the termination resistor; a second input resistor connecting the inverting input terminal to the second terminal on the termination resistor; an integrating capacitor connecting the inverting input terminal to the output terminal of the first operational amplifier; and wherein the first output of the differential input stage is connected to the first terminal on the termination resistor; and the second output of the differential input stage is connected to the input of the shunt feedback transimpedance amplifier.