• State TI Thinks Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 2 answers
  • Subscribers 29 subscribers
  • Views 225 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.

OPA1622: OPA1622

Ramgopal Divakar
Expert 1100 points
Part Number: OPA1622
Other Parts Discussed in Thread: INA1620

Hello,

I have to design an audio driver to drive a handset or headset:

Handset - 20 ohms and sensitivity 107 dB@1 mW

Headset - 625 ohms and sensitivity 112 dB@ 1mW

What op amp do you recommend? I saw the OPA1622 and it appears to be a good fit. I made a table below with SPL numbers and with this opamp if I power it at +/- 5V, I can go as high as 8Vpp it appears from the datasheet. 123 dB is fairly loud to the ear as the max output correct or do I need to go higher?

  • 0
    TI__Mastermind 18415 points

    Hello, 

    I am currently looking into your question and will respond by the end of business tomorrow. Thank you for your patience.

    Best Regards, 

    Chris Featherstone

  • 0
    TI__Mastermind 18415 points

    Hello, 

    The OPA1622 is a great choice for an audio driver. Looking up the decibel exposure levels for human hearing, 123dB is very loud. The information I am finding states that around 105 decibels/4min for a personal audio device at max volume is equivalent to a chainsaw level and would be considered to damage hearing if exposed too long. That being said I believe 123dB is more than sufficient headroom for an audio application. 94 dB/1hr is the average use of personal electronics based on the information I have found. 

    The linear output swing for a 32 ohm load on the OPA1622 is 2V from the supply rails at +/-5V. This is 3V positive and 3V negative or 6Vpp.  

    For heavier loads if you do find that you will need more power, we have an application note on parallel outputs to drive more current. It shows the INA1620, however the same technique can be used with any amplifier.  

    https://www.ti.com/lit/an/sboa352/sboa352.pdf?ts=1663697924554&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FINA1620

    Best Regards, 

    Chris Featherstone

  • 0 in reply to Chris Featherstone
    Expert 1100 points

    Thanks,

    yes you are right. I read about dB levels later so 112 dB should be enough pretty much worst case. On page 6, I see a swing of up to 800mV from the rails so shouldn't I get minus 4.2 to +4.2? This is for the 625 ohm earpiece in case I need it. It won't be anywhere close to this on the 20 ohm earpiece. 

    I will use this part,

    regards,

    Divakar

  • 0 in reply to Ramgopal Divakar
    TI__Mastermind 18415 points

    Divakar, 

    Yeah, for the lighter loads such as 600 ohms it will be 900mV from each supply rail. For 625 it will be about the same. The no load condition is 800mV. As you increase the load resistance to a heavier load (meaning more current) less than 600 ohms the output swing will reduce. The claw curve shows the output droop over current draw below. Although, keep in mind the plot below is tested by slamming the output into the rail. This is beyond the linear operation we specify for Aol and we pull current out of the device to see how "strong" the output stage is. I personally like this curve because it tells a lot such as how much current can be source and sunk on the device over temp before hitting current limit, where the output falls to 0V and the device can now longer drive a load. Between this and the Aol spec we get a lot of info for headphone drive capability. Let me know if I can help further with a schematic review when you are ready or have any other questions. 

    Sourcing Current:

    Best Regards, 

    Chris Featherstone

  • 0 in reply to Chris Featherstone
    Expert 1100 points

    Thanks, please add me as a friend so I can send the schematics for review later. 
    Thanks,

    Divakar

  • 0 in reply to Ramgopal Divakar
    TI__Mastermind 18415 points

    Divakar, 

    I just sent a friend request. Let me know if I can be of further assistance. 

    Best Regards, 

    Chris Featherstone