Audio Electronics - Cascodes, Folded Cascodes, and Current Mirrors (Part 3)

For those readers following the fascinating article series by Morty Tarr on "Cascodes, Folded Cascodes, and Current Mirrors," this final article in the series contains an additional section with important aspects of amplifier design. In the first two parts of this article series, Tarr discussed the technical merits of cascodes and related circuits. This useful addendum covers a simple test circuit for matching FET devices, the fascinating story of the Blowtorch Line Stage design, and additional notes on inverting and non-inverting amplifier stages and integrators. This article was originally published in audioXpress, December 2021.

In Part 1 of this three-part article about circuit topologies that are used to provide specific functions for an amplifier design, the author discussed cascodes and folded cascodes. In this Part 2, he focuses on current mirrors and line stages. As the author writes, “As designers, we have many devices to choose from. Some devices are ideally suited to certain tasks. Other tasks require performance that is difficult to achieve. While many excellent devices exist today, ideal devices do not exist, except maybe in Spice simulations.” This article was originally published in audioXpress, October 2021.

For this audio electronics article, Morty Tarr wrote a fascinating exploration of circuit topologies that are used to provide specific functions for an amplifier design. Cascodes, folded cascodes, and current mirrors are some of these topologies, intended to improve the performance of the devices, but which also add complications. In the first of a three-part series, the author discusses cascodes and folded cascodes, useful to improve high-frequency response and device linearity.

audioXpress December 2021 is now available. Learn how Room Correction and Speaker Calibration is influencing efforts towards the Self-Calibrating Loudspeaker, Dirac's take on Spatial Room Correction Technology, and how to Measure Directivity of In-Wall Loudspeakers. Richard Modafferi describes his unique crossover design build, Frans de Wit talks about DC Power Supplies, Morty Tarr discusses important aspects of amplifier design, and Michel Nieuwenhuizen offers an Arduino-based motor control for turntables. Start reading online or in print.

The November 2021 edition of audioXpress looks at the latest industry trends in digital signal processing, and enabling fully adaptive audio DSP experiences. Roger Shively (JJR Acoustics) writes about how the unique acoustic space of the car interior can be defined by the use of DSP, and Al Clark (CEO, Danville Signal Processing) shares his company’s journey into the development of the dspNexus DSP Audio Processor. Now available for viewing online, download and in print.

The October 2021 edition of audioXpress is now available in print and digital. This edition offers a balanced mix of content, starting with our annual market update report on home theater, and associated residential technologies. Brent Butterworth reviews a MEMS earphone design from USound, Geoff Hill completes his Tetrahedral Test Chamber Story, and Bruce Heran writes about refurbishing Altec Lansing Vintage Speakers. Diving into audio electronics, Morgan Jones writes about Ultra-Linear Design; Morty Tarr discusses Cascodes and Folded Cascodes; and Richard Honeycutt talks about the Effects of Negative Feedback. Jump right in!