THS4150EVM: Set gain for in phase and out of phase channel individually

Severin Getzner

Part Number: THS4150EVM

Hey, how do I control the gain of the output channels individually. So for example I would like to have the out of phase output to be 1/2 of the input signal voltage and the in phase output to be the same as the input signal voltage.
I already soldereed 10kR trim potetntiometers here (marked red in the picture), but those only control the the output voltage for both channels. (turning only one potentiometer controls both channels)

over 3 years ago

0 Michael Steffes over 3 years ago

Guru 48395 points

That is not how FDA's worrk, they will produce a certain differential signal that has equal amplitudes on each side but 180deg out of phase, but if you imbalance the feedbacks that will add a large CM component to the output swing.

0 Severin Getzner over 3 years ago in reply to Michael Steffes

Prodigy 220 points

Michael Steffes said:
That is not how FDA's worrk

But if I need to adjust the ratio because other elements in the chain will affect it in the opposite way, then how would you recommend to do it?

0 kai klaas69 over 3 years ago in reply to Severin Getzner

Guru 140200 points

Hi Severin,

then do it differently. Don't use a FDA but two standard OPAmps.

Kai

0 Alec Saebeler over 3 years ago in reply to kai klaas69

TI__Mastermind 23099 points

Hello Severin,

I would agree with Kai & Michael here; you should not use an FDA for this application. For FDAs and line drivers matching the feedback of both signal paths is absolutely critical.

Please take a look at our high speed standard op-amps (many of which have a dual package) to explore an option suited for your application.

Best,

Alec

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THS4150EVM: Set gain for in phase and out of phase channel individually