• State TI Thinks Resolved
  • Locked Locked
  • Replies 9 replies
  • Answers 1 answer
  • Subscribers 51 subscribers
  • Views 1071 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

3Volt to 10mVolt Conversion,Max current 1mA

Krishnamoorthy Baskaran
Prodigy 250 points
Other Parts Discussed in Thread: REF2912

Hi

I need to give 10mV as Op Amp Reference.Input Source voltage is 3.0Volt,i need to develop 10mV .

Advice me a suitable solution

  • 0
    Guru 243120 points
    The simplest solution would be a voltage divider, with the ratio 299:1.

    How much accuracy do you need? And what is the op amp's input bias current?
  • 0 in reply to Clemens Ladisch
    TI__Mastermind 30600 points

    Hi Krishnamoorthy,

    Do you have single supply or dual supply? If you have dual supply, you could do something like the following:

    The accuracy question is very important as well, the offset voltage is going to directly impact that. The first stage contributes Vos*(1+1/300) and the second stage contributes Vos*(1+1) so the total offset contribution is roughly 3*Vos. In my simulation (attached), a perfect 3V input gives a 10.4mV output, for an error of 4%.

    3Vto10mV.TSC

    If you only have a single supply, then you'll run into issues with producing such a low output voltage, most rail to rail op-amps can't get that low accurately.

    -Paul

  • 0
    TI__Guru*** 139956 points
    Krishnamoorthy,

    Is the 3V source accurate enough to directly get the 10mV reference? If not then what is the required accuracy for the 10mV?
    Is this 10mV used in just one location or more than one.? I ask because voltage drops on both the high and low side of the reference can be a significant error in voltage as it travels along the circuit board. 1mA is a significant load for a 10mV source, why is the current demand so high?
  • 0 in reply to Paul Goedeke
    Prodigy 250 points

    Thanks for the quick Reply

    My Source voltage 3.0 Volt from CR2032 Battery ( Single Battery only) ,The Input Voltage may decrease up to 2.3 or 2.4.

    Advice using Single Supply ,

    Thanks and Regards

    K.Baskaran

  • 0 in reply to Krishnamoorthy Baskaran
    TI__Guru*** 139956 points

    K,

    Coin cell battery means low current is imperative. I understand the power source now, but I don't know the load characteristic on the 10mV output. Until that is known, I can't fill in the something block with the best solution.

  • 0 in reply to Ron Michallick
    Prodigy 250 points

    Hi Ronald Michallick

    i plan to 10mV is as reference voltage of Amp input ,For the cost reduction Can use signle supply OP AMP or i have to go for dual supply OP Amp ?

    Pls see the image

    Regards

    K

  • 0 in reply to Krishnamoorthy Baskaran
    TI__Mastermind 30600 points
    Hi K,

    Your image didn't load - can you try again?

    -Paul
  • 0 in reply to Paul Goedeke
    Prodigy 250 points

    Hi Paul

    Cost reduction

    Can i go with Single supply OP Amp ( 3+Ve ref to Gnd)   OR

    I have to go for Dual supply Op Amp  ( + 3Volt and - 3Volt)

  • 0 in reply to Krishnamoorthy Baskaran
    TI__Mastermind 30600 points
    Hi K,

    All op-amps will take single or dual supply so the cost saving will come from the need to have two different supply rails on your board. The circuit I provided earlier assumed that you had a stable 3V input, but with the coin cell it won't work. Because you're just using it as reference voltage into an op-amp (basically no output current required), you may want to consider using a device like the REF2912 and a voltage divider to get to 10mV. Again, accuracy is going to be of some concern but it can be worked around.

    Your picture didn't load again. Are you using the "Insert Code, Attach Files and more..." link at the bottom of the screen? I find that using a jpeg for images works well and if you have a PDF version that will work too.

    -Paul