TLV4172: Strange Voltage Divider Value

Khoi Ly10

Part Number: TLV4172

Hi Ti Community,

I am using TLV4172 Single-supply op amp to act as a voltage follower for my voltage divider and the results doesn't look as expected.

Based on the voltage divider formula, we have 2.7K/ (2.7K+6.8K)*4V =1.14 V output.

However, I measured the output signal to be 2.9V using both osciloscope and my multimeter. The resistor values were also measured with the multimeter.

Is there any particular design consideration when using a single-supply op amp of this type?

Thanks and please let me know if you need some clarification

Khoi Ly

over 5 years ago

0 Tim Claycomb over 5 years ago

TI__Genius 15410 points

Hi Khoi Ly,

The way the voltage divider is setup the formula is 6.8k/(2.7k+6.8k)*4V = 2.86V. Try measuring the voltage on pin 10 (+IN3), you should measure about 2.86V.

If you want 1.14V output, you will need to switch R51 and R53 in your circuit.

Thank you,

Tim Claycomb

0 Tim Claycomb over 5 years ago

TI__Genius 15410 points

Hi Khoi Ly,

I also recommend reading "The Unused Op Amp - what to do?" for our recommendations on how to configure unused op amps in dual and quad packages.

Lastly, I recommend watching our TI Precision Lab videos. The videos on Input and Output Limitations will explain everything to take into consideration when using single supply operations.

Thank you,

Tim Claycomb

0 Khoi Ly10 over 5 years ago in reply to Tim Claycomb

Intellectual 620 points

Thank you so much,

I was so fixated into the single-supply design and worried about its common mode voltage that I made one of the simplest mistake. Thank you for catching that. I think there is nothing wrong with the setup other than the voltage divider placement then.

Khoi Ly

0 Tim Claycomb over 5 years ago in reply to Khoi Ly10

TI__Genius 15410 points

I'm glad we could help! If you need any additional support please let us know.

-Tim Claycomb

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TLV4172: Strange Voltage Divider Value