Anjan Chakravorty

A modified physics-based two-section model is proposed to accurately capture the lateral non-quasi-static effect in SiGe HBTs. A methodology is proposed to include the DC emitter current crowding effect in the existing two-section model framework. The proposed two-section model is implemented in Verilog-A. The large-signal transient and the small-signal AC simulations are carried out and the results are compared with the numerical device simulation data. The proposed model is observed to perform better than the existing two-section model and the state-of-the-art standard model from the perspectives of small-signal frequency-domain characteristics and large-signal transients.

The state-of-the-art and π-models for the lateral non-quasi-static (NQS) effect are analyzed. The superiority of the π-model to capture the lateral NQS effect is demonstrated through small-signal simulations of both the models, implemented in Verilog-A. A hybrid model is proposed and a corresponding formulation of the base impedance is obtained. The equation gives the base impedance of the state-of-the-art as well as the π-model under appropriate conditions. The methodology to implement the hybrid model in Verilog-A is discussed. The hybrid model shows significantly higher accuracy than both the state-of-the-art model and the π-model when compared with the device simulation data.

A two-section equivalent circuit model with hybrid topology is proposed to model the base impedance of SiGe HBTs. The formulations suitable for implementation in compact-model are obtained. A simpler yet accurate method is also proposed to implement the hybrid two-section model. The models are implemented in Verilog-A and small-signal simulations are carried out. The proposed models predict the small-signal lateral NQS effect more accurately than the existing models.