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OPA1632: Which operational amplifier should I choose? OPA1632 or LME49724 or THS4131 or others?

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Replies: 6

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Part Number: OPA1632

My audio codec can output 2Vrms differential signal, but I want to get a 8Vrms differential signal to driver my 600ohm load.

Which operational amplifier should I choose? OPA1632 or LME49724 or THS4131 or others?  

If the operational amplifier operates from a single power supply, how much  supply voltage does it need?

  • Hello Ke,

    What is the input common-mode and desired output common mode of your design?

    Best,

    Hasan Babiker

  • In reply to Hasan Babiker31:

    Hi Hasan,

    The codec's single supply voltage is 3.3V,  the common mode voltage of output signal is 1.65V. Maybe it can be ac coupled to the operational amplifier using a capacitor.

    If  the operational amplifier is operated from a single power supply Vcc, then the output common mode voltage can be mid-supply voltage which is 0.5*Vcc.

    I want to use the operational amplifier to drive a 600ohm headphone.

    Thanks and Regards,

    ke xu

  • In reply to ke xu:

    Hello Ke,

    All of these devices should be able to handle the design you have mentioned. The LME49724 seems to have the best THD+N performance for a 600 ohm load, out of the three parts. In terms of a single supply voltage, I would suggest using at least 12V for an 8Vrms output signal. You may need to increase this voltage further depending on the part and its output common-mode specs. 

    Best,

    Hasan Babiker

  • In reply to Hasan Babiker31:

    Hi Hasan,

    I am worry about the voltage output swing, because in the OPA1632 datasheet, we can see that voltage output swing is (V+) - 4.5 to (V-) + 4.5 when its RL is 800ohm. so if I want to get 8Vrms  output voltage with a 600ohm load resistor,maybe I should provide a 30V single supply voltage to OPA1632.

    Best regards,

    ke xu

  • In reply to ke xu:

    Hello Ke,

    The voltage output swing in a differential amplifier represents the swing each output can achieve. So in the case of the OPA1632, while each output can go between (V+ - 4.5) and (V- + 4.5), the actual differential output that can be achieved would be double that value.

    So in the case of a 8Vrms differential signal (which is about 11.32 Vpeak differential), each output of the amplifier (OUT+ and OUT-) would need to be able to achieve half of that differential signal. Each output of the amplifier would need an output voltage range between +5.66 & -5.66 or 11.32V & 0 for a single supply configuration. Taking into account the 4.5V to each supply would give us a total supply voltage of at least 20.32V single supply. You can apply this same logic to any of the other differential amplifiers as well. 

    Hope this clears things up.

    Best,

    Hasan Babiker

  • In reply to Hasan Babiker31:

    Hi Hasan,

    Thanks for your reply. I am clear about that now.

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