Tim Green's series on Op Amp Stability

Charles Sawabini

Other Parts Discussed in Thread: OPA4188

Several TI documents reference Tim Green's 15-part series on Operational Amplifier Stability. I have done extensive web searches, and have managed to find a few parts piecemeal. Is the entire series available anywhere? Please advise. Thanks.

over 10 years ago

0 Tim Green1 over 10 years ago

TI__Expert 6275 points

The basis of the article series can be found here:

http://e2e.ti.com/support/amplifiers/precision_amplifiers/w/design_notes/2645.solving-op-amp-stability-issues.aspx

En-Genius where the articles were originally published is no longer a Web Magazine. I attach the 11 parts completed in the zip file attached to this post.

Let me know if any questions. Thanks for your interest.

TG Stability_All pdf.zip

0 Ken Dillinger over 10 years ago in reply to Tim Green1

Expert 1220 points

When will be graced with parts 12 - 15?

-Ken

0 Tim Green1 over 10 years ago in reply to Ken Dillinger

TI__Expert 6275 points

Parts 12-15 will be included in the Op Amp Stability book in development. Hopefully, completed over the next two years. In the mean time we are here to support any op amp stability problems you may encounter....

Thanks for your interest in the technical writings.

0 Charles Cheng over 8 years ago in reply to Tim Green1

Prodigy 10 points

When will the operational amplifier stability book be launched?

This is a very good material of understanding op and stability.

Few material deals with this area.

Hope it will come in as soon as possible!

0 Tim Green1 over 8 years ago in reply to Charles Cheng

TI__Expert 6275 points

Book is still a work in progress. For now the link below has some good material put together by myself and my stability colleague, Collin Wells, that is a subset of the book. There are 4 parts to download.

http://e2e.ti.com/support/amplifiers/precision_amplifiers/w/design_notes/2645.solving-op-amp-stability-issues.aspx

0 Tony Wang over 7 years ago in reply to Tim Green1

Intellectual 310 points

Hi Tim,

any ideas about how to calculate the stability of a differential operational amplifier?

0 Ron Michallick over 7 years ago in reply to Tony Wang

TI__Guru*** 149776 points

Tim,

The op-amp doesn't know it's setup as differential (difference) operational amplifier.

None of the feedback goes to the non inverting input so it is not part of the stability analysis.

Treat this amplifier setup the same as any other amp op circuit.

0 Angelica Zamora over 7 years ago in reply to Tim Green1

Prodigy 120 points

Hi!

I am using the "Rate-Of-Closure" Stability criteria (Part 1 of 4) to analyze some different opamp networks at different temperatures. A weird behavior is occurring at low temperatures, at -40°C using OPA4188:

In the plot above I am showing the loop gain graph for 25°C and -40°C. For the case of -40°C, since 1/beta is above Aol. My interpretation is: it means that there is no margin for Aol to fix 1/beta, so the circuit is unstable at -40°C, isn't it?

We have tested a small lot in the lab (not isolated but connected to some others) and in some cases it has shown to be unstable (not all times, in every circuit of the lot), so I am looking forward to substantiate theoretically why we are observing such behavior.

Thank you very much for your help.

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Tim Green's series on Op Amp Stability