Design and implementation of bias sequence circuits for GaN HEMT amplifiers both pulsed and CW applications

GaN HEMT with silicon substrate is famous and considered as the next generation of RF power transistor technology. It has major advantages of high power, low cost and reliability etc., GaN HEMT requires special attention in bias circuit to avoid the instability of the device. Sequence circuit is required to supply voltages in order. In this paper, we have design and implemented the sequential circuits in bias network for pulsed and CW applications. MAX881R is used in power supply for pulsed while LTI1964ES5-BYP with R2D Recon 2405 is used for high current application in CW. For pulsed applications in ON sequence the gate is turned-on ~ 220 ms before the drain, while in OFF sequence the drain is turned-off ~ 1.7 s before the gate. While in CW applications in ON sequence the gate is turned-on ~ 130ms before the drain and in OFF sequence, the drain is turned-off ~ 633ms before the gate.