Graphene Transistor-Based Active Balun Architectures

While different RF functionalities, such as an amplifier or a mixer, have been designed using the graphene FET (GFET) devices, the balun circuit has not been explored. In this paper, two innovative active balun architectures are presented taking advantage of the GFET's unique symmetrical and ambipolar behavior, respectively. The symmetry-based active balun circuit is realized using an advanced SiC-based GFET RF technology. After circuit design and optimization using a large signal GFET compact model, the circuit has been fabricated and characterized. Measurement results confirm its excellent functionality. Circuit simulation shows that the second architecture exploring the GFETs ambipolar behavior gives equivalent results compared with the first architecture. Both topologies avoid asymmetric impedance matching and result in the accurate amplitude and phase balance of the balun.