Added Noise in Oscillators Caused by the Transistor Base Emitter Breakdown Phenomenon

Abstract

When increasing the RF power level in transistor oscillators to achieve better phase noise performance a reverse voltage breakdown of the base emitter junction of the oscillator transistor can occur. This results in increased phase noise and long term-transistor degradation. Common transistor simulation models/simulators do not have this effect included in their library, so the simulations fail to predict correct oscillator behavior. Starting from common oscillator topologies and active devices the critical waveforms were analyzed and related to the generated noise spectra. A theoretical explanation of the breakthrough process will be given, and the simulation models will be enhanced. Finally, recommendations are made how to avoid breakdown effects and the active device degradation in practical designs.

Keywords:

• Avalanche
• Base
• Bipolar
• Breakdown
• Emitter
• Oscillator
• Phase noise
• Transistor

Acknowledgements

This work would not have been feasible without the possibility to measure the phase noise of oscillators precisely using the Rohde & Schwarz FSWP26 phase noise analyzer supplied by the BTU. Sample crystals were provided by Bernd Neubig of AXTAL, as well as measurements of space grade crystals on specialized equipment. Alexander Roth from Rohde & Schwarz supplied some test oscillators and valuable advice on the operation of the FSWP phase noise analyzer. Prof. Ignaz Eisele from the University of the Armed Forces in Munich helped in explaining some breakdown and noise mechanisms in RF semiconductors as well as the influences of modern fabrication technologies on noise performance. Markus Müller from the Institut für Grundlagen der Elektrotechnik und Elektronik, Dresden, Germany for enlightening discussions about parameter extraction of packaged devices. Richard Kaußler (personal communication) allowed me to use his photographs and videos of transistor base-emitter breakdown luminance effects. With his equipment he was able to demonstrate breakdown luminance in several transistors including the 2N2222A used in this paper. More reverse engineered transistors and ICs can be seen at his webpage https://www.richis-lab.de/.

Additional information

Notes on contributors

Wolfgang Griebel

Wolfgang Griebel received his Dipl Ing from Vienna Technical University, Vienna, Austria in 1983. He is now pursuing his PhD at the Brandenburg Technical University in Cottbus, Germany at the Institute for Radio Frequency and Microwave Techniques, working on ultra-high stability space grade crystal oscillators at a frequency of 5 MHz.

Matthias Rudolph

Matthias Rudolph received his Dipl-Ing in electrical engineering from the Berlin Institute of Technology, Berlin, Germany, in 1996, and Dr-Ing degree from Darmstadt University of Technology, Darmstadt, Germany, in 2001. In 1996 he joined the Ferdinand-Braun-Institut, Leibniz Institut für Höchstfrequenztechnik (FBH), Berlin. In October 2009, he was appointed the Ulrich-L.-Rohde professor for RF and microwave techniques at Brandenburg University of Technology, Cottbus, Germany. His research focuses on modeling of FETs and HBTs and on design of power, broadband, and low-noise amplifiers. He authored or coauthored 70 publications in refereed journals and conferences and “Introduction to Modeling HBTs” (Artech House, 2006), and coauthored “Nonlinear Transistor Model Parameter Extraction Techniques” (Cambridge University Press, 2011) and “RF / Microwave Circuit Design for Wireless Applications”, second edition (John Wiley & Sons, 2013). Dr Rudolph is actively involved in the IEEE activities. Email: [email protected]

Ulrich L. Rohde

Dr Ing-habil Ulrich L Rohde is a Honorary Fellow of IETE & Fellow of IEEE and member of several professional societies that includes Member of the Board of Trustees Fraunhofer Gesellschafts (EMFT) for Solid State Technology, Member of the Board of Trustees of the Bavarian Academy of Science, and Honorary Member of the Academy of Science, and ETA KAPPA NU Honor Society. His contributions are distinctive, made significant advancement of technology for industrial growth and the benefit of society, published more than 350 papers, 4 dozen patents, dozen books, and over dozen awards for scientific inventions. Email: [email protected]