INA1620EVM: Board mods required for 18dB of gain, with +-15v supply powering the board.

Mike Davis

Part Number: INA1620EVM

Hello,

I’m just wondering what mods need done to the INA1620EVM board in order to achieve 18dB gain, without any filtering? If possible I’d like to only utilize the internal chip resistors.

Thanks,

Mike

over 5 years ago

0 Tamara M Alani over 5 years ago

TI__Genius 10850 points

Hi Mike,

The device is configured for unity gain. In order to change this to 18dB (7.94V/V), you will need external resistors. This is explained in section 3.1 of the INA1620EVM guide: http://www.ti.com/lit/ug/sbou205/sbou205.pdf

Select resistors such that R1=R7 and R2=R6 and R2/R1 = 7.94:

-Tamara Alani

0 Mike Davis over 5 years ago in reply to Tamara M Alani

Prodigy 230 points

Hi Tamara,

Thank you. So are you saying R2 & R6 could = 15.88, and R1 & R7 could = 2? Or R2 & R6 could =7.94, and R1 & R7 could + 1? And I would get the same result either way?

And are these resistors in kOhms? Then of course the right channel would mirror the left channel.

Thanks,

Mike

0 Tamara M Alani over 5 years ago in reply to Mike Davis

TI__Genius 10850 points

Hi Mike,

I would recommend using either, but in k-ohms.

-Tamara

0 Mike Davis over 5 years ago in reply to Tamara M Alani

Prodigy 230 points

Ok thank you!!

0 Mike Davis over 5 years ago in reply to Tamara M Alani

Prodigy 230 points

Hi Tamara,

1 more question. If feeding this board with a single ended source, would you tie the negative to the ground on the source end? And if you wanted 7.94v of gain using a single ended source, what value of resistors would you use in R2 &R6 if a 1kohm resistor was used in R1 & R7? Or would the ratio between the resistors change altogether?

Thanks,

Mike

0 Tamara M Alani over 5 years ago in reply to Mike Davis

TI__Genius 10850 points

Hi Mike,

Thanks for your post! A picture is worth 1000 words. Can you draw out what you are intending to do and I can help you review it?

-Tamara

0 Mike Davis over 5 years ago in reply to Tamara M Alani

Prodigy 230 points

Hi Tamara,

I would draw a picture, but it's very simple to explain what I want to do. Connect a single ended DAC to the INA1620EVM board, and achieve 8V of gain. What I tried was connected the ground leg together with the negative. However it seems doing this I have only achieved around 4V of gain rather than 8V using a 8kohm resistor in R2 & R6, and a 1Kohm resistor in R1 & R7. So would I need to use a 16Kohm resistor in R2 & R6 since the source is single ended? Or should I be using different values altogether in those positions to balance things out?

Thanks,

Mike

0 Tamara M Alani over 5 years ago in reply to Mike Davis

TI__Genius 10850 points

Hi Mike,

Please see the following note on how to configure unused op amps: http://www.ti.com/lit/an/sboa204a/sboa204a.pdf

In split-supply (which is what you have) you want to connect the output to the inverting input (Out B to In- B) and connect the non-inverting input to ground.

-Tamara

0 Mike Davis over 5 years ago in reply to Tamara M Alani

Prodigy 230 points

Hi Tamara,

That's not the question I was asking. But it was also very useful information so thank you. I'm pretty sure I'm doing things right by connecting my single ended source ground leg to both the ground and the inverting input pin. As my DAC is single ended, I do not have an inverting leg to connect to the inverting input on the INA1620EVM.

Thanks,

Mike

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INA1620EVM: Board mods required for 18dB of gain, with +-15v supply powering the board.