This thesis presents the design and implementation of an active inductor using gallium nitride technology. This design is largely motivated by the lack of high quality varactors in GaN. Active inductors are therefore proposed as an alternative to varactors as an impedance tuning mechanism in GaN which will act as the building block for tunable circuits such as VCOs, filters, phase shifters etc. The fabrication of such tunable circuits in GaN will in turn allow for highly integrated complete RF systems on chip in GaN.
Furthermore, the design and implementation of a tunable bandpass filter with amplitude and frequency control making use of the aforementioned active inductor is presented. The active inductor's measured tuning range at 3.5GHz is 8 to 20nH with a quality factor greater than 200. To the authors' knowledge, this is the fifirst active inductor and bandpass fifilter implemented in GaN.