Equivalent Circuit Establishments of a GaN High-Electron-Mobility Transistor and 635 nm Laser Diode for a Short-Pulsed Rising Current Simulation

Abstract

In this paper, a dynamic operational linear regulator (DOLR) based on a GaN high-electron-mobility transistor (HEMT) and wide-bandwidth operational amplifier was developed and implemented. The driving current could be regulated and controlled by the DOLR for 632 nm laser diodes. The constant-current mode for the continuous-wave laser and the pulse-width modulation (PWM) mode for the short-pulsed laser were realizable using this DOLR. This study focused on the rising-edge time change on the laser driving current when the DOLR was operated under the high-frequency PWM mode, because the parasitic components on the GaN HEMT, laser diodes, printed circuit board, and power wires could influence the current’s dynamic behavior. Therefore, the equivalent circuit models of the laser diode and GaN HEMT were applied to establish a DOLR simulation circuit in order to observe the rising-edge time change on the laser driving current. A DOLR prototype was achieved, and so experimental waveform measurements could be implemented to verify the DOLR simulation and operation.