Fully Coupled Electrothermal Mixed-Mode Device Simulation of SiGe HBT Circuits

It is well known that for the design and simulation of state-of-the-art circuits thermal effects like self-heating and coupling between individual devices must be taken into account. As compact models for modern or experimental devices are not readily available, a mixed-mode device simulator capable of thermal simulation is a valuable source of information. Considering self-heating and coupling effects results in a very complex equation system which can only be solved using sophisticated techniques. We present a fully coupled electrothermal mixed-mode simulation of an SiGe HBT circuit using the design of the A709 operational amplifier. By investigating the influence of self-heating effects on the device behavior we demonstrate that the consideration of a simple power dissipation model instead of the lattice heat flow equation is a very good approximation of the more computation time consuming solution of the lattice heat flow equation.