TLV2371 - the phase margin and the gain margin

Hirotaka Matsumoto

Other Parts Discussed in Thread: TLV2371

Hi all

Would you mind if we ask TLV2371?
We measured the phase margin and the gain margin using Middle brook method as following.
20150220_TLV2371_stablitytest.TSC

So, we could not get the phase margin and the gain margin.
If you have some advice, could you let know us?

Kind regards,

Hirotaka Matsumoto

over 9 years ago

0 John Caldwell over 9 years ago

TI__Genius 12325 points

Hello,
One issue I see immediately is that the Vcom voltage was 5V which is also the positive supply voltage. With the op amp saturated at the positive rail the simulation will not run properly. Try changing Vcom to 2.5V and running your simulation again.

0 Tim Green1 over 9 years ago

TI__Expert 6275 points

Attached is TINA schematic with Loop Gain measured. We do not use Middlebrook method but propose an easier way. For discussion of this and op amp stability look at 4 parts in following link:

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

TLV2371 Loop Gain.TSC

0 Hirotaka Matsumoto over 9 years ago in reply to John Caldwell

Guru 27525 points

John san,

Thank you for your reply!
Ok, we got it!

Kind regards,

Hirotaka Matsumoto

0 Hirotaka Matsumoto over 9 years ago in reply to Tim Green1

Guru 27525 points

Tim san,

Thank you for your reply!

We have one question.
The gain margin is the value which is in case of phase 0.
(We can see that the gain margin is 20dB.)

However, frequency is over 3MHz(Band width).
So, in this case, you mentioned 8.88f, could you let know us how to get this value?

We need your help.

kind regards,

Hirotaka Matsumoto

0 Hirotaka Matsumoto over 9 years ago in reply to Hirotaka Matsumoto

Guru 27525 points

Tim san,

We are sorry that our last contribution may make you confuse.
You shows the phase margin, so about the gain margin, we can get it by the figure or AC test.

Kind regards,

Hirotaka Matsumoto

0 Tim Green1 over 9 years ago in reply to Hirotaka Matsumoto

TI__Expert 6275 points

The gain margin can also be read from the loop gain circuit I sent. See attached paper from: faculty.mercer.edu/.../GainMarginandPhaseMargin.pdf

GainMarginandPhaseMargin.pdf

0 Hirotaka Matsumoto over 9 years ago in reply to Tim Green1

Guru 27525 points

Tim san,

Thank you for your cooperation.

Hirotaka Matsumoto

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TLV2371 - the phase margin and the gain margin