Patent ID: 9054485
Filing Date: 2015-06-09
Classification: H01S

Abstract:
1. A two-terminal-modulating laser diode driver comprising: an anode connection for connecting to an anode terminal of a laser diode; a cathode connection for connecting to a cathode terminal of the laser diode; wherein the laser diode has a turn-off time that is longer than a turn-on time; a source-follower transistor connected to conduct an anode current between a power supply and the anode connection; a first control signal applied to a gate of the source-follower transistor for modulating the anode current; a cathode driver transistor connected to conduct a modulating current between the cathode connection and a source node; a second control signal applied to a gate of the cathode driver transistor for modulating the modulating current; and a signal generator, receiving an input signal that indicates when the laser diode is to be turned on to illuminate, and when the laser diode is to be turned off to not illuminate, the signal generator activating the first control signal and the second control signal when the input signal indicates that the laser diode is to be turned on, the signal generator de-activating the first control signal and the second control signal when the input signal indicates that the laser diode is to be turned off; a bias current generator, coupled to the cathode connection, for drawing a bias current through the laser diode; wherein the bias current flowing through the laser diode is insufficient to illuminate the laser diode and is smaller than the modulating current; wherein the bias current sets an operating point for the laser diode and for the source-follower transistor, wherein the bias current is also drawn through the source-follower transistor in series with the laser diode; wherein the source-follower transistor is modulated to conduct the anode current when the input signal indicates that the laser diode is to be turned on, and to not conduct the anode current when the input signal indicates that the laser diode is to be turned off; wherein the cathode driver transistor is modulated to conduct the modulating current when the input signal indicates that the laser diode is to be turned on, and to not conduct the modulating current when the input signal indicates that the laser diode is to be turned off, wherein both the cathode terminal and the anode terminal of the laser diode are modulated and whereby the laser diode and source-follower transistor are biased to the operating point by the bias current.