This technical note from Texas Instruments explores the benefits of using high density, high-precision Digital to Analog Converters (DACs) and Operational Amplifiers (OPAMPs) in laser drive applications. It will demonstrate that with these devices and some discrete components, a high precision solution can be created and easily modified to accommodate different current-output requirements and power-supply specifications.
The DAC80508 and OPA2376 from Texas Instruments will be used to illustrate the functionality of this application.
Laser diodes generally require a precisely controlled current to regulate their output power. It is advantageous for this current to be adjustable as output power can change over temperature. For this reason, a DAC can be used to dynamically update the forward current. In addition, a low-noise source is desired to reduce the intensity noise (instability in the output power) of a laser output.
Current-output DACs that can drive hundreds of milliamps are uncommon, so a voltage-output DAC with a voltage-to-current (V/I) converter can be used to create a high-side current source to drive the laser diode.
To read the full paper, click here.