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OPA2348 | Not working for instrumentation op amp

Other Parts Discussed in Thread: OPA2348, UA741, OPA348

Hi all,

I am using OPA2348 to amplify my differential signal by implementing a instrumentation amplifier.But it is not working for me.When i am implementing the same circuit with UA741,I can able to get the exact output as per my defined gain.In OPA2348 I can able to get the output for the differential amplifier(i.e) Get the difference for the two signals and then amplification is done by means of two resistors.

My question:

1)Whether the OPA2348 can be used as a instrumentation op amp?

2)Is there any specific circuit for OPA2348 for implementing the instrumentation op-amp?

Reference: I took the instrumentation circuit from "http://en.wikipedia.org/wiki/Instrumentation_amplifier"

Kindly clarify my doubts.

Thanks & Regards,

Karthick.

  • Hello Karthick,

    Provided the amplifiers are operating in their linear region I see no reason why the OPAy348 would not work.  I have attached a few slides from one of my presentations that may help.

    In comparing the OPAy348 and UA741 I noted that the UA741 can source 4 times as much current as the OPAy348.  This current will depend on the gain setting resistor and input differential voltage as shown in the presentation.  I would verify that the OPA is not required to source too much current.  Also, please note the difference in supply voltage requirements between the devices and ensure that the OPAy348 is powered with no more than 5.5V.

    Finally, we do manufacture a variety of instrumentation amplifiers and difference amplifiers.  They have integrated laser-trimmed resistors to ensure good CMR and gain error.  The prefix for these devices is "INA" and they are located under Products->Amplifiers and Linear->Difference Amplifier (or Instrumentation Amplifier).

    IA.ppt
  • Karthick,

    Any op amp, including OPA348 can be used to implement an instrumentation amplifier but care needs to be taken not to violate the input common-mode voltage range and output swing, which is especially easy to do while operating on a single supply - see below.  As you change the gain or move from a dual supply to a single supply operation, pay special attention do VCM, VREF, VT1 and VT2 so that they always stay within the supply voltage (see attached). 

    OPA348 INA.TSC