H.S. Black: Feedback
Feedback, or its application by humans as control theory, despite the protestations of audio designers that eschew its use, is an entirely natural phenomena. Every time you reach out to pick up an object, get up and walk around, or write something on a piece of paper, feedback data from multiple body sensors are being […]
Measuring TIM
This paper by Leinonen, Otala and Curl investigates the measurement of TIM, a hot topic in the 1970’s and early ’80’s after its potential to cause sonic degradation by the incorrect application of feedback around high loop gain solid state amplifiers. Now days (2017), there is a very complete and thoroughly in-depth understanding of TIM […]
A Concise Overview of TIM by Bob Cordell
This set of articles was written in the early 1980’s by Bob Cordell, a few years after Matti Otala (RIP) identified TIM (Transient Inter-Modulation) as the probable cause of sonic imperfections in high feedback solid state amplifiers in the 1970’s. Otala’s paper sent shock waves through the amplifier design community but sadly it ended up […]
The Monolithic Op-Amp: A Tutorial Study
This was an invited paper at the ISSCC in 1974 by James Solomon, who at the time worked for National Semiconductor (acquired in 2011 by TI). Those were heady days in semiconductors, with major process and circuit design breakthroughs taking place at breakneck speed. The general purpose microprocessors’ pivotal role in powering the Apple II […]
Marshall Leach Opamp Tutorial
Marshall Leach (RIP) was a Professor of Electrical Engineering at Georgia Tech University best known for his Leach Amplifier which he used as a practical vehicle for teaching his students the finer details of analog design, feedback, thermal compensation and power electronics. Hundreds of Leach Amplifiers were built over the years by his students, […]
The Alexander Amplifier
Mark Alexander’s eponymous creation was an early example of a high performance CFA amplifier and used an ADI integrated opamp and IGBT output devices in a novel circuit configuration that, at the time, yielded vanishingly low distortion and blistering speed. The ‘Alexander’ amplifier has been recycled by practitioners numerous times since its initial publication with […]