Visible-Laser Driver Has Digitally Controlled Power Modulation

Abstract: The circuit in the figure below includes a 10-bit digital-to-analog converter (DAC) with 3-wire serial input that operates and maintains a visible-light laser diode at constant average optical output power. A separate digital input line (MOD) enables a comparator with open-drain output (IC4) to implement digital communications by pulsing the laser-diode through Q1.