An ultrahigh performance laser driver based on novel composite topology enhanced Howland current Source

Laser diodes (LDs) are used in a wide range of applications, such as optical wireless communications and LIDAR. To meet the demanding requirements of LDs for high accuracy and stability of the injection current, a high-precision, high stability LD driver with overvoltage protection is proposed. A novel structure based on enhanced Howland current source is described: composite topology enhanced Howland current source (CTEHCS), which has the advantages of high precision, high stability, and extensive regulation range. A 20-bit DAC and high-precision reference source are used to form a front-stage DAC circuit for precise and stable voltage reference. A closed-loop feedback calibration loop is applied to eliminate significantly the absolute errors and auxiliary calibrating of the effect of power operational amplifier on the temperature rise of critical devices. An innovative overvoltage protection circuit is designed for the load side of the CTEHCS, and the protection range can be flexibly set to 4/5/6 V to avoid damage to loads such as LDs. The noise performance, accuracy and stability, modulation bandwidth, nonlinear error, overvoltage protection performance, and turn-on and turn-off time of the experimental prototype are described in detail.