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INA1651EVM: Question

Jerry Gorman
Prodigy 300 points
Part Number: INA1651EVM
Other Parts Discussed in Thread: INA1651

Is the audio performance listed in the INA1651 EVM guide based on the actual EVM design. In most cases using ceramic caps in the audio path like this EVM does is generally avoided as these caps are not considered to be very good for audio.  Even TI avoids them and has advised against using them at the input of TPA32XX because of potential performance issues.  Just curious because the audio performance numbers in the EVM guide look great.      

  • 0
    TI__Expert 6250 points

    Hi Jerry,

    It is a good idea to avoid using high-k ceramic capacitors (e.g. Y5V or X7R dielectrics) in filtering applications, as their voltage coefficient will contribute distortion to the signal. C0G or NP0 dielectric ceramics are recommended for these applications.

    Where this becomes somewhat less clear-cut is in AC-coupling applications such as the INA1651 EVM inputs. In these cases, a large capacitance is required in order to minimize the high-pass corner frequency of the AC-coupling. This in turn requires using either a high-k ceramic capacitor, as C0G/NP0 capacitors aren't usually available in the required capacitance range. However, in an AC-coupling application (particularly into a high-impedance input such as the INA1651), the signal doesn't affect the bias across the capacitor very much. Since the distortion mechanism for high-k ceramics is primarily a voltage coefficient of capacitance, the fact that there is very little voltage change works in our favor.

  • 0 in reply to Alexander Davis
    TI__Prodigy 300 points

    Thanks for the detailed response.