Is OPA1652 stable with gain of 0.5

Chris Woolrych

Other Parts Discussed in Thread: OPA1652

I wish to use a OPA1652 to convert from a differential/balanced audio input to an unbalanced output (using a standard three op amp configuration as per circuit below to do this).

To ensure that the gains are correct through the system I require that the overall gain is set to 0.5 (ie in differential stage where R3=R2/2 from circuit below, Input buffers are unity gain).

Are you able to confirm that the OPA1652 will be stable with this gain of 0.5. Would also note that will be driving internal circuitry so load capacitance is minimal.

The data sheet states that stable for unity gain but am aware that phase margin reduced for successively lower gains.

I could look at implementing different configuration with inherent 0.5 gain but would prefer to use circuit shown below.

Image result for standard balanced to unbalanced circuit

Thanks

Regards

Chris

over 8 years ago

0 John Caldwell over 8 years ago

TI__Genius 12325 points

Hi Chris,

From a stability standpoint, the "gain" is always the "noise gain" of the amplifier, which is measured from the non-inverting input. The gain from the non-inverting input of an op amp is G = 1+ Rf/Rg, meaning that the "noise gain" can never fall below 1, and a unity gain stable op amp is actually stable for signal gains less than one. In your example, the noise gain of the OPA1652 is 1.5. Here is a blog post that my former colleague Bruce Trump wrote: e2e.ti.com/.../the-inverting-attenuator-g-0-1-uh-oh-is-it-unstable

0 Chris Woolrych over 8 years ago in reply to John Caldwell

Prodigy 160 points

Hi John,

Thanks for the quick response and clarifying this issue for me.

Chris Woolrych

0 John Caldwell over 8 years ago in reply to Chris Woolrych

TI__Genius 12325 points

Anytime Chris! I hope the OPA1652 works well for you.

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Is OPA1652 stable with gain of 0.5