Resources for circuit design with
current-feedback operational amplifiers.

Nick Alexeev

If you are designing with high speed op-amps, you should be aware of current-feedback (CFB) op-amps. You may run into a CFB op-amp without knowing. A statement in a datasheet "... behave much like standard voltage feedback operational amplifiers" is not the same as "classical voltage feedback architecture". These quotes come from two different op-amp datasheets. It turned out that the first amplifier is a CFB, although the datahseet didn't state it explicitly.

CFB op-amps can be faster than VFB, and CFB op-amps have faster slew rates. But CFB op-amps have caveats which are different from the familiar VFB op-amp caveats.

A good place to start familiarizing with current-feedback operational amplifiers is the chapter in The Art of Electronics: The x-Chapters by Horowitz & Hill. The authors aren't affiliated with a semiconductor company, so they don't have to sugar coat. The chapter has a section on when to use CFBs, which ends with this rule of engagement: Our general advice is to use VFBs for pretty much everything other than the special applications for which CFBs excel. [section 4x.6.4]

Sergio Franco wrote in defense of current feedback amplifiers (2017), and a series of articles about CFB op-amps: introduction, characteristics, applications and limitations (2019).

Practical current feedback amplifier design considerations (archive)
Intersil application note AN1106 (1993)

Current feedback amplifier theory and applications (archive)
Intersil application note AN9420 (1995)

An intuitive approach to understanding current feedback amplifiers (archive)
Intersil application note AN9787 (1998)

Converting from voltage-feedback (VFB) to current-feedback amplifiers (CFB)
Intersil application note AN9663 (1999)

Current feedback op-amp applications circuit guide
National Semiconductor OA-07 (1988)

Current feedback amplifiers
National Semiconductor application note 597 (1989)

Frequent faux pas in applying wideband current feedback amplifiers (mirror)
National Semiconductor OA-15 (1990)

Voltage feedback (VFB) vs. current feedback (CFB) op-amps
Texas instruments application report slva051 (1998)

A current-feedback op-amp circuit collection
Texas Instruments application report sloa066 (2001)

The book Op-amps for everyone has a chapter on current-feedback op-amps (chapter 8).
by Ron Mancini (editor in chief) at Texas Instruments slod006 (2002)

Current Feedback Amplifiers Part 1 (Analog Dialog 30-3), Part 2 (Analog Dialog 30-4)
by Erik Barnes at Analog Devices (1996)

Current feedback (CFB) op-amps
Analog Devices tutorial MT-034 (2008)

High speed current-feedback op-amps
Analog Devices tutorial MT-057 (2008)

Choosing between voltage feedback (VFB) and current feedback (CFB) op-amps
Analog Devices tutorial MT-060 (2008)

© Copyright 2023, Nick Alexeev