Analysis And Characterization Of Thermal Effects In Analog Circuits

Dielectrically Isolated Bipolar Junction Transistors (DIBJTs) are used in industry for high speed and high power applications. These devices suffer from thermal heating and are subjected to change in their characteristics. This thesis explores the thermal effects involving the self heating and inter-device heating (thermal coupling) at the device as well as at the circuit level. Systematic analysis of individual device heating characteristics in a particular Current feedback operational amplifier (CFOA) design is carried out, using the VBIC (Vertical Bipolar Inter-company) model in the the Cadence SpectreS simulator. A diagnostic and design procedure is established for circuit designers to determine the possible causes of the thermal tail and to eliminate the problem. To consider the inter-device heating effects, a BJT symbol including adjacent device heating in the VBIC model is developed at the schematic capture level. Different test structures are developed, and fabricated using National Semiconductor process to study dependence of inter-device heating of DIBJTs on various layout factors. An innovative method for the inter-device heating measurement is developed using IC-CAP / HPIB interfaced evaluation system.