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OPA333: Precision Amplifiers Forum

user4861027
Prodigy 40 points

Part Number: OPA333
Other Parts Discussed in Thread: ADS1262, LM7705, OPA388

Hi,

Power supply is 5v-0,v+ is 5V,v- connect to ground.and my circuit is below，IN+ connect to 0-5V voltage source,and IN- connect to 2.5V.can I have a -2.5V to 2.5V output？

  • 0
    TI__Mastermind 23050 points

    Hi,

    You cannot obtain a negative output without a negative supply. The op amp can only output voltages that are within the range of the supplies. Furthermore, even in a rail-to-rail topology, you will never be able to fully swing the output to the rails. For the OPA333 you can get as close as 50mV, but if you need to be able to swing all the way from -2.5V to +2.5V on the output, you will need supplies that extend slightly beyond this range. Hope this helps!

    Regards,

    Zak Kaye

    Precision Amplifiers Applications 

  • 0 in reply to Zak Kaye
    Prodigy 40 points
    Hi, Zak, thanks for your responding. And do you have any recommended high-precision op amps that can achieve this function? The input signal is 0-5V, the output signal range of 0-2.5V(or -2.5V to +2.5V), op amp's output is ads1262 acquisition.
  • 0 in reply to user4861027
    TI__Mastermind 44760 points
    Hi,

    As Zak mentioned, you would need to supply wider supply voltages to be able to output 0-5V. One possible solution is to use an LM7705 to generate a slightly negative supply rail for the op-amp so that the output can go to 0V; however, you would still to provide a larger positive supply voltage for the op-amp to drive up to 5V.

    Another important consideration...The ADS1262 is a very low-noise ADC and most any op-amp you place in front of it will have higher noise. If you want to achieve the best resolution with the ADS1262, then I would suggest using an even lower noise op-amp such as the OPA388. The next best option would be not to use an op-amp at all; otherwise, you're likely to degrade the system resolution.

    Best Regards,
    Chris