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WEBENCH® Tools: opamp request for measuring input voltages which one to select.

Bastiaan Pierik75
Intellectual 370 points
Other Parts Discussed in Thread: OPA2990, TLV9051, TLV6742, TLV9001, TLV9061, TLV2471, OPA365, TINA-TI

Tool/software: WEBENCH® Design Tools

Dear support, researchers,

i have a question,

I am using the following DC drivers from polulu,

and the

one has a offset of 50mV and 10mV/A and the other roughly 140mV/A, the 140mV/A is for dc motors and an Electromagnet

the maximum current I have set for the Peltiers I am going to use is 20A. the max current possible is 15.7A at 25V.

12 bits ADC from the new Teensy4.1.

which op amp in single supply is best for such an easy application

I would like to create the maximum range for the input of the ADC possible.

20A =3.3V

0A=0V with 50mV offset.

200mV max input on the opamp +50mV offset.

so the total input voltage on the inverting opamp will be 0.25V with offset = gives me an 13.2 V amplification.

Best

Bastiaan

  • Former Member
    0 Former Member

    Hello Bastiaan,

    What type of supply voltage are you expecting to need?  I suppose you will need greater than 13.2V as you are looking for that voltage at the output?

    If you could provide us with a few more details of application, then we might be able to make a more specific recommendation.

    A popular choice in this space would be the OPA2990.  I think you may find it to be of interest.

    Regards,

    Daniel

  • 0 in reply to Former Member
    Intellectual 370 points

    Hey Daniel,

    Thanks for the quick reply.

    I am looking for a single supply opamp with 5V. To drive

    50mV as input  which should give me  0V on the output, and at 250mV it should be at 3.3V on the output

    Do I use the y=Mx +b positive to calculate the amplification and resistor values?

    Thanks for looking into this.

    Best Bastiaan

  • Former Member
    0 Former Member in reply to Bastiaan Pierik75

    Hi Bastiaan,

    Ok.  I misread and thought you wanted 13.2V at the output.  Then, you'll want a low voltage op amp, most likely.

    Then I would say it depends on other factors such as bandwidth and output current needed.  Popular choices include TLV9001, TLV9051, TLV9061, TLV6742, and others depending again on speed and accuracy.

    What does your input signal look like?  Is it a sinusoidal?

    One option is to AC couple the input to the non-inverting input of the op amp and provide a DC offset with a voltage divider.  Then, you use the resistors to gain up the signal.  It would help to know more about your input signal, however.

    Regards,

    Daniel

  • 0 in reply to Former Member
    Intellectual 370 points

    I am reading out a current sensor inside a chip, so mostly I think the current isnt varietying that much it should be linear.

    a few questions do I have: are there calculators that allow me to calculate single supply opamps with an ADC if I have all the values?

    based on the TLV2471

    www.ti.com/.../sloa030a.pdf

    can I use this calculation to set the output voltage over a range close to 0...3.3V. however I saw that the OPA365 also can be used with a true ground,

    but can this opamp be used for the same SLOA30a.pdf for CASE 1 Y=mx+b? 

    I would like to check the signal maybe 1x second nothing fancy.

  • Former Member
    0 Former Member in reply to Bastiaan Pierik75

    Hello Bastiaan,

    We have a tool which will help you to decide how much bandwidth and accuracy your op amp will need for certain ADC configurations.  The Analog Engineer's Calculator can be downloaded online and used as shown below to help with op amp calculations for your ADC.

    Where exactly are you seeing Y=mx+b in the application note?  The formula you will need to use will depend on the configuration of your circuit.  Yes, the OPA365 can go all the way to GND and may be a reasonable choice for an accurate device for an ADC.

    Regards,

    Daniel

  • 0 in reply to Former Member
    Intellectual 370 points

    Ok many thanks!

    I was allready looking for something like that.

    Do you have a general page for all component calculators/tools offered by TExas instruments?

    Best

    Bastiaan

  • Former Member
    0 Former Member in reply to Bastiaan Pierik75

    Hi Bastiann,

    I'm happy to help, although I'm not sure that we have a single page.  But, we have several resources.

    FAQ for GPAMPs - This site has a list of resources.  The stuff at the top is more of the tools.

    TI Precision Labs – Videos for new & experienced engineers

    TI Analog Pocket Reference Guide – Quick reference for key concepts

    The Signal – Collection of expert blogs on op amp concepts

    Amplifier Macromodels - TINA-TI SPICE simulation software for design verification

    Filter design tool

    Amplifier Quick Search - Search for a part or search by circuit

    Let me know if you need any further help or have any further questions.

    Regards,

    Daniel