Adaptive Bias-Sequencing Circuit for GaN-based RF Power Amplifiers

The advantages of Gallium Nitride (GaN) technology in terms of thermal efficiency with wide bandgap, low stray capacitance & ON resistance, higher cut-off frequencies & breakdown voltage makes it an ideal choice for RF power amplifier design. One challenging aspect in the use of GaN transistors is the provision of bias voltages in specific timing sequence. This is typically achieved through specialized circuits to ensure a thermally stable operation. This paper presents the design and implementation of a biasing circuit based on gate switching with closed loop adaptive temperature compensation functionality including the corrections in the earlier work. The rise and fall time between bias point and pinch-off of 800 nanoseconds has been achieved with power amplifier temperature stability around 55 degrees Celsius.