SBOA092A –October 2001
HANDBOOK OF OPERATIONAL AMPLIFIER APPLICATIONS
Bruce Carter and Thomas R. Brown ABSTRACT While in the process of reviewing Texas Instruments applications notes, including those from Burr-Brown – I uncovered a couple of treasures, this handbook on op amp applications and one on active RC networks. These old publications, from 1963 and 1966,respectively, are some of the finest works on op amp theory that I have ever seen. Nevertheless, they contain some material that is hopelessly outdated. This includes everything from the state of the art of amplifier technology, to the parts referenced in the document – even to the symbol used for the op amp itself:
These numbers in the circles referred to pin numbers of old op amps, which were pottedmodules instead of integrated circuits. Many references to these numbers were made in the text, and these have been changed, of course. In revising this document, I chose to take a minimal approach to the material out of respect for the original author, – Thomas R. Brown, leaving as much of the original material intact as possible while making the document relevant to present day designers. Therewere some sections that were deleted or substantially changed: •= •= “Broadbanding” operational amplifier modules – replaced with discussion of uncompensated operational amplifiers. Open loop applications and Comparators – Applications showing an operational amplifier used open loop, as a comparator have been deleted. At the time of original publication, there were no dedicated comparatorcomponents. Good design techniques now dictate using a comparator instead of an operational amplifier. There are ways of safely using an operational amplifier as a comparator – if the output stage is designed to be used that way as in a voltage limiting operational amplifier – or if clamping is added externally that prevents the output from saturating. These applications are shown. Testing OperationalAmplifiers – a section that had become hopelessly outdated. Testing techniques are now tailored to the individual amplifier, to test for parameters important to its intended purpose or target end equipment.
•= Some other application circuits were eliminated – if they were deemed impractical in the light of today’s technology.
This handbook has also been reorganized toeliminate some redundancy, and place all application circuits in one location. The reader is cautioned that proper decoupling techniques should be followed with operational amplifiers. Decoupling components are omitted from applications schematics in this document for clarity. Consult reference 2 for proper decoupling techniques. I also cleaned up grammatical and spelling mistakes in the original. ---Bruce Carter, Texas Instruments Applications (Excerpts from) Thomas Brown’s original Preface: The purpose of this handbook is to provide a single source of information covering the proper design of circuits employing the versatile modem operational amplifier. This manual will be helpful to the experienced user of operational amplifiers, as well as the new user, in extending the range of potentialapplications in which these devices can be used to advantage. It is assumed that the reader will have a basic knowledge of electronics, but no particular knowledge of operational amplifiers is needed to use this handbook. The operational amplifier is treated as a circuit component inherently subject to certain rules of operation. The design of the operational amplifiers themselves is consideredonly when necessary to describe their less evident properties. Readers with a working knowledge of operational amplifiers will want to refer directly to the circuit collection. Readers whose job functions have not previously brought them in contact with operational amplifiers will want to proceed directly through the handbook until the desired degree of familiarity is obtained. Refinements are...