LT1014: stability for attenuator application

FRANK1

Part Number: LT1014

Hi Sir,

A customer has a inquire about stability when LT1014 is used as attenuator.

The application note warns that using op amps as attenuators can cause instability when tageting high frequency applications in tens of MHz range.

But we applied the LT1014 to the circuit that senses the output through the PWM driver in the 50kHz range, and ask for advice on whether this cause instability.

i want to know stability.

Thanks a lot.

Regards,

over 4 years ago

0 kai klaas69 over 4 years ago

Guru 140200 points

Hi Frank,

we definitely need a schematic from you

It should also include information about what load is connected to the output of LT1014. I mention this because capacitive loads can make trouble and may need a phase lead compensation in the feedback loop of LT1014.

Kai

0 Michael Steffes over 4 years ago

Guru 48395 points

hey Frank, eventually you might want a TINA LT1014 sim, there a 3 diff. models in V11 library - pick one,

Also, here is a more recent discussion of attenuators, you can always get them stable even if you start out oscillating.

https://www.planetanalog.com/are-inverting-attenuators-with-voltage-feedback-op-amps-inherently-unstable-and-why-might-you-want-to-apply-them-insight-11/#

0 Thomas Kuehl over 4 years ago

TI__Guru* 93105 points

Hi Frank1,

We definitely need to see a schematic for your LT1014 based attenuator circuit as Kai mentioned. The LT1014 is a unity-gain stable op amp and even though you plan to apply it as an attenuator having a gain less than 1V/V, the circuit noise gain will be slightly higher than 1 V/V. Therefore, unless there are added capacitances at the op amp output, or at the op amp input summing junction, it is probable that the LT1014 will remain stable.

Once we see your schematic to make a better determination.

Regards, Thomas

Precision Amplifiers Applications Engineering

0 Innbeom Seo over 4 years ago

Prodigy 25 points

Hello, Frank.

On june 7th, the circuit diagram was replied to by email.

I ask for futher answers.

Thanks.

0 Thomas Kuehl over 4 years ago in reply to Innbeom Seo

TI__Guru* 93105 points

Hi Frank,

Did you receive the schematic for the LT1014 attenuator circuit from Innbeom? If you did and it can't be shared on the e2e, then provide it to me via the TI internal email. Otherwise, please post it here on the forum where everyone who has shown interest in this thread can review and comment on it.

Regards, Thomas

Precision Amplifiers Applications Engineering

0 Innbeom Seo over 4 years ago in reply to Thomas Kuehl

Prodigy 25 points

Hello

Thank you for your response,Thomas Kuehl.
Can I send the schematic to you via email and discuss this issue in private?
Due to the schematic is confidential, and I can not post it in public forum.

0 Thomas Kuehl over 4 years ago in reply to Innbeom Seo

TI__Guru* 93105 points

Hello Innbeom,

Please send me an e2e friend request. Once I accept your request you will be able to contact me confidentially. We can exchange email addresses.

Regards, Thomas

Precision Amplifiers Applications Engineering

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LT1014: stability for attenuator application