Effect of lateral structure parameters of SiGe HBTs on synthesized active inductors

The effect of lateral structure parameters of transistors including emitter width, emitter length, and emitter stripe number on the performance parameters of the active inductor (AI), such as the effective inductance L_s, quality factor Q, and self-resonant frequency ω ₀ is analyzed based on 0.35-μm SiGe BiCMOS process. The simulation results show that for AI operated under fixed current density J_C, the HBT lateral structure parameters have significant effect on L_s but little influence on Q and ω ₀, and the larger L_s can be realized by the narrow, short emitter stripe and few emitter stripes of SiGe HBTs. On the other hand, for AI with fixed HBT size, smaller J_C is beneficial for AI to obtain larger L_s, but with a cost of smaller Q and ω ₀. In addition, under the fixed collector current I_C, the larger the size of HBT is, the larger L_s becomes, but the smaller Q and ω ₀ become. The obtained results provide a reference for selecting geometry of transistors and operational condition in the design of active inductors.