The Thermal Effects Of Self Heating Of Transistors On Analog Amplifier Design And Evaluation

Electrothermal effects play a major role in the performance of modern silicon-on-insulator (SOI) bipolar junction transistors (BJTs). This research work examines the influence of electrothermal feedback within a single device and within a circuit composed of such devices. Specifically, the frequency-domain thermal effects of self-heating in SOI BJTs on the performance of analog integrated circuits, with emphasis on current mirrors, and current-feedback operational amplifiers (CFOA), are investigated through analytical formulation, simulation, and measurement.For the extensive analysis and characterization of self-heating thermal effects, the Vertical Bipolar Inter-Company (VBIC) models for SOI BJTs are developed from fundamental physical device considerations. Extensive simulations have been done to validate the models using the SPECTRE simulator. Analytical formulations for the output impedance of the current mirrors, designed using SOI BJTs, are developed incorporating the effect of dynamic self-heating. This shows that a thermally induced "zero-pole doublet" in the transfer function of the output impedance can show a peaking effect in the frequency response. Such thermal effects have been demonstrated through frequency-domain measurements, using a precision impedance analyzer (Agilent 4294A) and an impedance probe (Agilent 42941A), on the test structures of current mirrors, fabricated using the VIP10TM bipolar process technology. Self-heating tolerant current mirror topologies are identified and verified experimentally. Self-heating influenced parameters of the conventional CFOA are identified through both analytical formulations and simulations. The analysis shows that the frequency response of the open-loop transimpedance, common-mode rejection ratio (CMRR), and power supply rejection ratio (PSRR) of the CFOA can be influenced by the dynamic self-heating. The techniques to design self-heating tolerant CFOAs are proposed, and their performances are demonstrated through simulation. Two new optimized topologies of CFOAs are designed and fabricated using the VIP10TM bipolar process technology as test chips, and frequency-domain and time-domain thermal effects are verified through extensive measurement. The verification of the thermal tail and the thermally induced longer settling time in the step response of the CFOA, in the non-inverting unity gain configuration, is accomplished through a time-domain measurement using an Agilent Infiniium DSO81204B digital oscilloscope, along with an 1169A InfiniiMax II series probe amplifier.