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OPA1678: OPA1678 reference design

Hailiang Zhang
Genius 11020 points
Part Number: OPA1678
Other Parts Discussed in Thread: OPA1637, INA1650, LM27762, OPA1656

Hi Team,

I would like to ask how to connect the IC audio output to the OPA1678 with differential left and right channels? Is there a reference circuit? Thanks!

Regards,
Hailiang

  • 0
    TI__Mastermind 25080 points

    Hey Hailang, 

    The OPA1678 can do this however I have provided additional examples since I don't know much information regarding the application. If you need further assistance for a specific design I would be happy to help. I would need some preliminary information. 

    • What is the supply voltage?
    • Gain?
    • What is driving the input signal/s?
    • Is the input fully differential in?
    • In the image above what is HPLP, HPLN? 
    • What is the OPA1678 driving for a load?

    If you need a fully differential input and output we have devices such as the OPA1637 fully differential amplifier (FDA). The INA1650 could also be used. 

    OPA1637:

    https://www.ti.com/product/OPA1637

    OPA1678:

    INA1650:

    https://www.ti.com/lit/ds/symlink/ina1650.pdf?ts=1712762488435&ref_url=https%253A%252F%252Fwww.google.com%252F

    Let me know if I can be of further assistance. 

    Best Regards, 

    Chris Featherstone

  • 0 in reply to Chris Featherstone
    TI__Genius 11020 points

    Hi Chris,

    • What is the supply voltage? Battery provide to LM27762
    • Gain? -22dB~8dB (Glass-G)
    • What is driving the input signal/s?  38mW stereo headphone amplifier differential ouput
    • Is the input fully differential in? L/R differentia, OP ouput can use the single-end
    • In the image above what is HPLP, HPLN?  L/R differential
    • What is the OPA1678 driving for a load? 32ohm

    Pls refer to the block diagram.

    Regards,
    Hailiang

  • 0 in reply to Hailiang Zhang
    TI__Mastermind 25080 points

    Hello Hailiang, 

    The OPA1656 may be better suited because it has more output current drive capabilities. I have put together a simulation showing a possible topology that is differential in and out. I have attached the simulation to the bottom of this post. The gain is set to 8 V/V. The gain could be adjusted by changing the feedback resistors, specifically R346 and R1.  The challenge is if the gain needs to be adjustable. A potentiometer can be used however I created impedance matching on each input. If the feedback resistor is adjusted resistors R355 and R5 should also be adjusted to match the feedback resistors. This may not be an issue but I wanted to point it out. 

    OPA1656.TSC

    Best Regards, 

    Chris Featherstone