Bias current and main pulse current for the PCX-7420

To minimize the laser diode’s response time to a pulse, the PCX-7420 can deliver current pulse in two steps. The first step is the bias pulse, which starts before the intended trigger time. The idea is to set the bias current just below the laser diode trigger point (the current can be set from 1 […]

Why is there overshoot and ringing on my current pulse?

Overshoot and ringing is the result of inductance. It’s everywhere, from PC board traces and component leads to the laser diode and its cable. An inductor stores energy in a magnetic field. When the current changes — such as during the leading and trailing edges of the pulse — the changing magnetic field creates a […]

Is it okay to ground one side of my laser diode?

It’s important that you NOT ground either the anode or the cathode of your laser diode for several reasons: A closed-loop laser diode driver needs to measure the output current accurately. A path to ground diverts a portion of the current, making the measurement (and thus the output current) inaccurate. A ground path reduces the […]