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Is there a better Amplifier available now than the TLC07x?

Other Parts Discussed in Thread: TLC071, TLC072, TEST, OPA1642, OPA172, OPA827, OPA1688

Hello,


I am designing a new audiometer (for hearing testing) and our old design uses the TLC072 and TLC071 amplifiers in the output stage of the audio. I am wondering if there is a better amplifier available that has the same capabilities as this but is more immune to EMI.

Our current design with these amplifiers is not completely immune to RF interference and I want to make the new one as immune as possible. I saw that there is EMIRR testing performed on the TLC07x Amplifier but I am not sure if the results are enough to make sure the new design is immune?

(www.ti.com/.../sboz022a.pdf)

Please let me know if these test results are in fact reliable enough and that RF inference shouldn't be a factor if I design with the TLC07x or if there is a new better Amplifier that has at least the same capabilities of the TLC07x?

  • The link is supposed to be for:

    • Technical Brief
      • SBOZ022A– September 2012 –Revised November 2012
      • TLC071EMI Immunity Performance
  • The OPA164x, for example OPA1642 has much better EMIRR if every thing else about it matches your application
  • Hi Jake,

    Can you tell me what supply levels you plan to use, what unity-gain bandwidth is needed and if the high output current is needed for the application? We may have some options with lower voltage amplifiers if one of them could be used.

    Regards, Thomas

    PA - Linear Applications Engineering

  • Hi Thomas,

    I am not worried about the unity-gain bandwidth but I am concerned about the output current. I need something that is close to the TLC07x output high current. (The OPA164x seems to have enough but more would be ideal.)

    I currently plan on using a Dual and Single Opamp with a +5V single supply and then a Single Opamp with a single supply of +15V. The +15V supply Opamp is the most important as it will be handling the audio signal in the output stage. The other +5V Opamps are for the Microphone talkover and for dividing 5V to 2.5V. Thank you,

    -Jake
  • Hi Jake,

    I reviewed all of our Precision Analog operational amplifier products and the high output current and high EMIRR requirements really reduce the number of amplifiers that we can suggest. I must say that after reviewing possible candidates that the high-current output op amps in general don't have high EMIRR and their graphs showing their EMIRR vs frequency are similar. That is understandable because they weren't necessarily designed with high EMIRR performance as a requirement.

    In practice you may find that the TLC07x and OPA164x, and other op amps with similar output current capability react differently when exposed to the same EMI conditions. They do have different levels of EMIRR performance at different frequencies. It just comes down to their individual EMI sensitivity at a particular EMI frequency.  You may want to take a look at the datasheets and EMIRR reports for the OPA827, OPA1688 and OPA172 amplifiers. All of these have pretty high output current capability.

    Often, it makes sense to try and incorporate EMI filtering in the circuit, before the op amp input. Doing so allows one to tailor the input filter response for maximum rejection of an offending EMI signal. Then any EMIRR provided by the op amp is a bonus. If I were redesigning a circuit for an update that would seem a good opportunity to include EMI filtering on the board. Something as simple as an appropriately selected ferrite input chokes (possibly a ferrite bead), followed by an X2Y capacitor across the op amp inputs, can creates a 2nd-order low-pass filter that can be quite effective in keeping conducted EMI from reaching the op amp's input.

    Regards, Thomas

    PA - Linear Applications Engineering