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US09054485B1 Asymmetric edge compensation of both anode and cathode terminals of a vertical-cavity surface-emitting laser (VCSEL) diode 有权
垂直腔表面发射激光器(VCSEL)二极管的阳极和阴极端子的非对称边缘补偿

Asymmetric edge compensation of both anode and cathode terminals of a vertical-cavity surface-emitting laser (VCSEL) diode
Abstract:
A laser driver circuit compensates for non-linear behavior of Vertical-Cavity Surface-Emitting Laser (VCSEL) devices. A VCSEL has an internal parasitic capacitance that is charged while the VCSEL is on. When the VCSEL turns off, this internal parasitic capacitor discharges, keeping the VCSEL on longer, increasing the physical turn-off or fall time. The laser driver circuit compensates for the slower fall time by modulating both anode and cathode terminals of the VCSEL as the VCSEL is turned on and off. Both plates of the internal parasitic capacitor are discharged at turn off, cutting the parasitic discharge time in half. A cathode driver transistor modulates the cathode voltage while a source-follower transistor modulates the anode voltage. A modulating current may be switched using a current mirror structure. Multiple source-follower transistors may be selectable in parallel, with switches to select the total anode current, allowing for programmable compensation of the fall time.
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