THS3491: Unity gain setting

Ryuuichi machida

Part Number: THS3491

Hello,

I would like you to confirm whether THS3491 can accept unity gain setting or not.
Because, according to datasheet, it seems that all spec is defined as 5V/V condition.
Could you please tell me concern about unity gain setting usecase ?

BR,

over 3 years ago

0 Alec Saebeler over 3 years ago

TI__Mastermind 24524 points

Hello BR,

Please see the two linked posts, where my colleagues discuss the implications and options of operating the THS3491 at unity gain:

Unity Gain Discussion: https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/735365/ths3491-minimum-gain-of-ths3491

Stability at Lower Gains: https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/762308/ths3491-ths3491-stability-at-low-gain-levels

Best,

Alec

0 kai klaas69 over 3 years ago

Guru 140200 points

Hi Ryuuichi,

300% overshot for all feedback resistors doesn't look unity-stable:

ryu_ths3491.TSC

I wouldn't do that, even if the simulation isn't telling the whole truth.

Kai

0 Michael Steffes over 3 years ago in reply to kai klaas69

Guru 48395 points

Well you can get it to work, but not sure why? for the output current and slew rate? Here I added a 150MHz pole at the V+ input - it also prefers a heavier load, so 200ohm for now, and boosted the Rf to 2k for phase margin improvement,

And the step response, not super pretty, but has a zero in the response - not unstable,

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THS3491: Unity gain setting