INA 2321

zoltan.fuszenecker

Hello,

I have got an INA 2321 differential amplifier and I don't understand something. As far as I know, the output is V_o=V_REF+G*(V_IN+-V_IN-) and V_o cannot be bigger than the supply power V_S =(V₊-V_-). G is the Gain, (V_IN+-V_IN-) is the differential input. I use V_S=5 Volts referred to the ground=0 V. If the amplified signals that interest me are between 16-21 Volts with the chosen gain, can I use a V_REF=-16 Volts? Then I would have an output that is 0-5 Volts referred to the -16 Volts reference. This way the output will not be bigger than V_S and I will be able to measure the signals I want.

Thanks for the answer!

Zoltán

over 12 years ago

0 Pete%20Semig over 12 years ago

TI__Mastermind 25865 points

Hello Zoltan,

If the device is connected to 5V single supply, the absolute maximum voltage for the inputs (including Vref) is -0.5V (please see table on page 2 of the data sheet). Therefore you cannot connect Vref to -16V.

Can you give us some additional information about the nature of your input signal? I'm interested in the signal's origin (does it come from a sensor?), frequency, and impedance.

0 zoltan.fuszenecker over 12 years ago in reply to Pete%20Semig

Prodigy 40 points

Hello,

thanks for the answer. That's basically what I wanted to know. The input comes from a Hall sensor with a frequency of 7 kHz and 50 mV amplitude.

Zoltán

0 zoltan.fuszenecker over 12 years ago in reply to zoltan.fuszenecker

Prodigy 40 points

Hello again.

I have yet another question. On page 3 of the datasheet it writes: Input vs. temperature +/- 7 uV/Celsius degrees. If I had a gain=200 than 1 C temperature increase causes +0,007*200=+1,4 mV Voltage growth on the output?

Thanks for the answer

0 Pete%20Semig over 12 years ago in reply to zoltan.fuszenecker

TI__Mastermind 25865 points

Hello Zoltan,

Your calculation is correct. Please be aware that the drift is relative to 25C.

There is a lot of information on this topic throughout the E2E forums. I suggest searching for "offset drift". Please let me know if you have any further questions.

0 qianlong fj over 12 years ago

Prodigy 10 points

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0 zoltan.fuszenecker over 12 years ago in reply to qianlong fj

Prodigy 40 points

Thank you, again!

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INA 2321