Opamp architecture VS practical usage

M

maxporter

Junior Member level 2
Joined
Dec 14, 2010
Messages
23
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,283
Activity points
1,477
Good morning,

Recently I've been looking into Opamp/OTA design. While there are tons of readings available, most are quite theoretical. But I’m kind of lost which architecture is best for certain applications. Does anybody know some good literature, which not only explains the OTA/Opamp, but also it’s practical usage and pitfalls? To give an example, which I’m currently looking at: a non-inverting opamp. Could a two stage OTA (5T OTA + CS output stage) work, is a single ended folded cascode opamp a better choice etc?

Thanks in advance
Max
 

Sort by date Sort by votes
I'd bet that most op amp vendors have selection guide app notes.
There are texts out there, op amp cookbooks and op amp principles.
But unless this is idle curiosity, let the application point you at what
you specifically need to know. You can spend a lot of time reading
stuff that is true and not immediately helpful. Which is fine if you've
got leisure time, but not fine if you're on the clock.
 

Upvote 0 Downvote
Thanks for responding, I really appreciate it.
Idle curiosity, true. I tend to overthink things. Regarding the app notes of vendors: my interest was chip design related, not so much application. So, for example the non-inverting opamp/buffer which I mentioned: I guess topology choice is not something I can distill from app notes?
Regards,
Max
 

Upvote 0 Downvote
A lot of the time "secondary" interests drive the selection of style
and finer params then, to choose between surviving candidates.

For example an extremely high BW and no great concern for Vio,
you might pick a CFA; inside a PWM controller, the controlled weak
output current of a OTA can easily be overridden or summed-to.

Generally a datasheet will highlight the intended application and
the top-line benefits the part claims to deliver.
 

    M

    maxporter

    Points: 2
    Helpful Answer Positive Rating
Upvote 0 Downvote
An excellent resource is the Linear Databook and its variations. Published by National Semiconductor Corporation. Comprehensive (or close to it) list of IC's. A vast portion are op amps. Descriptions, specs, operating tips, graphs, schematics and sample applications. Updated every year or so. My 1982 edition is 2000 pages, 3 inches thick.

We widen our knowledge of electronics by perusing lists like the above book, as well as supply catalogs. It's vital to discover what is the range of available devices. It's a springboard for ideas about making our own projects and inventions.

Among the variety of Linear databooks is one devoted to op amps. New and old copies seen on Ebay and Amazon.

In addition to op amps of the everyday style, there are:

* instrumentation amplifiers
* rail-to-rail output type
* Norton type (current inputs rather than voltage inputs)
* Audio amplifiers (example LM386, TDA 2002)
* Radio functions
* Comparators (presents a path to ground)
 

    M

    maxporter

    Points: 2
    Helpful Answer Positive Rating
Upvote 0 Downvote
Thanks, I will definitely check it out.
 

Upvote 0 Downvote
archive.org has a pile of IC databooks, scanned and ready.

Older is often better, for applications content. I've noticed the
"back matter" in datasheets is getting real thin, sometimes zero,
while old National databook part pages might have several dozen
application figures and pages of eyeball charts for non-line-item
behaviors. TI versions of those datasheets are pretty thin.
 

Upvote 0 Downvote
Upvote 0 Downvote
Thanks all for the feedback so far. Will have to reserve some reading time, to distill my needs.
Regards,
Max
 

Upvote 0 Downvote
You must log in or register to reply here.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…