Analysis of Electrothermal Effects in Bipolar Differential Pairs

• Published in: IEEE transactions on electron devices Vol. 58; no. 4; pp. 966 - 978
• Main Authors: d'Alessandro, Vincenzo, La Spina, Luigi, Nanver, Lis K, Rinaldi, Niccolò
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.04.2011; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amplifiers; Analog circuits; Applied sciences; Asymmetry; bipolar junction transistor (BJT); breakdown voltage; Circuit properties; Circuits; Devices; differential pair; Distortion; Electric, optical and optoelectronic circuits; Electronic circuits; Electronic equipment and fabrication. Passive components, printed wiring boards, connectics; Electronics; electrothermal simulation; emitter-coupled logic; Exact sciences and technology; heterojunction bipolar transistor (HBT); Hysteresis; impact ionization; Integrated circuit modeling; Isothermal processes; Junctions; Mathematical analysis; Mathematical models; Radicals; Resistors; self-heating; silicon germanium (SiGe); silicon-on-glass (SOG); Simulation; Studies; Testing, measurement, noise and reliability; thermal coupling; thermal instability; Thermal resistance; Transistors; Voltage measurement; Analog circuit; electrothermal simulation; Emitter coupled logic; Voltage current curve; Differential amplifier; Ge-Si alloys; Glass; Transmitter; Feedback regulation; Voltage control; Junction transistors; Thermal instability; Thermal resistance; Disruptive voltage; Feedback; breakdown voltage; Testing equipment; Self heating; Impact ionization; Silicon; Heterojunction bipolar transistors; Resistor; heterojunction bipolar transistor (HBT); Binary alloy; Damaging; Semiconductor alloys; Thermal behavior; Analog circuits; Bipolar transistor; emitter-coupled logic; differential pair; thermal coupling; Analytical method; Germanium; self-heating; silicon germanium (SiGe), silicon-on-glass (SOG); bipolar junction transistor (BJT)
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2011.2106132

An extensive experimental and theoretical analysis of bipolar differential pairs subject to radical electrothermal feedback is presented. Measurements demonstrate that considerable thermally-induced degradation of circuit characteristics may occur, eventually turning into the full disappearance of a linear region, which is replaced by a hysteresis behavior under voltage-controlled conditions. An analytical model is derived for a simple yet reliable prediction of the distortion of I- V curves. A more elaborated circuit approach is employed to accurately quantify the concurrent destabilizing action of electrothermal and impact ionization effects, as well as to evaluate the impact of layout asymmetries and examine the beneficial influence of emitter degeneration resistors. Simulation results are found to compare favorably with experiments performed on silicon-on-glass test structures with various layouts and isolation schemes, from which the benefits of thermally coupling the two devices become evident.