Feedback in Analog Circuits

Agustin Ochoa received his B.S. from the University of Arizona in 1971, his M.S. from Stanford University ('72), and returned to the University of Arizona for his Ph.D. ('77) in electrical engineering with minors in physics and mathematics. He began his working career at Sandia National Laboratories in Albuquerque New Mexico working on CMOS technology development, radiation hardening, and device issues. In 1986 he joined Hughes Aircraft in Carlsbad California where he became manager of their BiCMOS development group. His interests throughout his career have been in device physics, in transform mathematics, and in analog circuits. In 1990 he left Hughes Aircraft to join a small analog design startup, Technology Applications Group, leaving his senior device position to become a junior analog designer-the perfect combination of math, device behavior, and analog circuitry, thinking that in a few years he would learn all he needed to be a full analog designer. Then he had to face feedback. After a review of analog texts and many discussions with other designers he developed an approach to circuit analysis (DPI/SFG) combining the Driving Point Impedance technique of Ruben Kelly (Univ. of New Mexico) with Signal Flow Graphs (Sam Mason). Dr. Ochoa continued developing and applying the DPI/SFG methodology for circuit analysis with particular application to feedback systems in his work at ABB Hafo, Brooktree/Rockwell/Conexant, Fairchild Se miconductor, Xtreme Spectrum, Zarlink, Ramtron/Cypress Semiconductor, and now as an independent consultant as Xtreme Analog Circuit Technology (XACT), working on classic and very low power analog amplifiers, reference cells, regulators, plls, crystal oscillators, active filters, RFID development, and elements of RF.

Introduction to circuit analysis.- The DPI/SFG method- simple circuits.- Small Signal Modeling, Signal Flow Graph Algebra.- Feedback 1.- Feedback 2.- Finding Equivalent Noise Sources.- Oscillator Circuits.- Other subsystems: PLL's, Switched Capacitors.- High Frequency Circuits-LNAs, Mixers.- Some aspects of Scattering Parameters.