Karingada, Arun Thomas2011-07-142011-08-242011-07-142011-08-242011-07-14January 20http://hdl.handle.net/10106/5654Silicon Germanium (SiGe) hetero junction bipolar transistors (HBTs) are used in a variety of circuits like analog mixed signal and RF(radio frequency ) circuits. As the device gets smaller these days the self heating affects the performance of the SiGe HBTs. This paper uses theoretical methods based on device geometry and material properties to calculate the thermal resistance and thermal capacitance of SiGe HBT. In addition to theoretical estimations time domain, frequency domain and DC measurements are done on National Semiconductor's CBC8 HBTs which is used to extract the values of thermal impedance parameters.enM.S.