Temperature Scalable Modeling of SiGe HBT DC Currents Down to 43K

Of critical importance to successful circuit design is accurate device models. At present, designers of electronics for extreme environment electronics are using the same device models used by general purpose electronics designers, which only work between -55◦C to 120◦C. In some cases, the temperature dependences of device parameters are turned off, and device parameters are extracted to only fit measured data at a single temperature. One may repeat this for several temperature points to obtain “isothermal” model parameters. Clearly this approach does not allow self-heating. More importantly, such models cannot be used to design circuits that require continuous description of device performance over temperature [1], such as the bandgap reference circuit, a fundamental circuit block critical to reliable operation over a wide range of temperature of numerous analog, digital, and mixed-signal circuits. This work presents improved equations for the collector and base currents, with an emphasis on lower temperature operation down to 43 K.