Design of a broadband microwave BJT active inductor circuit

The synthesis and S-parameter analysis of a novel broadband microwave active inductor circuit utilizing bipolar junction transistors (BJTs) are presented. The circuit realizes inductance by impedance gyration using a CC-CE pair, with the parasitic capacitance between the base and emitter of the CE transistor as the load. A feedback network consisting of two parallel RC networks in series is used to produce a flat inductance versus frequency response by compensating for the π model elements of the transistors. Using the S-parameters of NEC NE57800 transistors (fτ≃6 GHz), an analysis of the proposed circuit predicted an inductance of 4±1 nH and a resistance of less than 14 Ω up to a frequency of 2.5 GHz. The resonant frequency of the circuit was computed to be about 3.45 GHz. An integrated version of this circuit could prove to be useful for monolithic microwave integrated circuits using BJTs