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Maximum input voltage

Thread Summary

The user inquires about the MAX9814's VIN_MAX = 100mVp-p (THD 1%) and its behavior with AGC enabled. The final answer clarifies that this specification applies when AGC is disabled, and enabling AGC can prevent distortion even with higher input voltages. For Figure 1, it is likely that the gain is set to 40dB, and AGC can eliminate distortion from inputs of 160-180mVp-p.
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Category: Datasheet/Specs
Product Number: MAX9814

Hello

My customer intends to choose MAX9814.

1)

Would you  please let us know  about  the MAX9814's Maximum Input Voltage VIN_MAX = 100mVp-p (THD 1%) means?

My understanding is, the condition in this case is GAIN = VDD (set to 40dB), and if an input higher than this is applied, the output will begin to distort, even with the AGC enabled.

Is this correct?

So, if the GAIN is set to Unconnected (60dB), the input must be reduced to, say, 10mVp-p or less, or the output will be distorted even with the AGC enabled.

Is this correct?


2)

Looking at the left side of Figure 1 on page 8 of the data sheet, even when an input of 160-180mVp-p, which is higher than 100mVp-p,

is actually applied, enabling the AGC eliminates distortion.

Is the GAIN condition in this case GAIN = VDD (40dB)?

The Maximum Input Voltage VIN_MAX=100mVp-p has a margin, so even with an input of 160-180mVp-p, if AGC is enabled, distortion will be eliminated.

Am I correct in understanding this?

Best Regards

  • Hello, see my comments below:

    1) VIN_MAX = 100mVp-p (TYP) with the condition THD = 1% means, as you described, that the output will distort further if > 100mVp-p input signal is applied (with the EC Table Global Conditions that GAIN = VDD, giving 40dB gain). However, this is the case for AGC disabled. If enabled, the amplifier will adjust the output level so as not to clip according to AGC parameters such as attack time, hold time, release time, and threshold.

    2) Regarding Figure 1, although the gain is not specified for that plot, it seems reasonable that 40dB was used, because that is the EC Table Global Condition, and based on the slew rate and amplitude of the left-most (clipped) output level. As you estimated, it appears that the input is ≈ 160mVp-p judging from the divisions of the oscilloscope's vertical scale. Looking at the clipped output level, the 1V/div vertical divisions, and where the sine wave is cut-off on the peak and trough, it appears that the amplitude would be 16Vp-p. This corroborates with the fact that the other gain options are 50dB and 60dB, which would result in ≈316X and 1000X gains.

    I hope this answers your inquiry. If not, let me know. Thank you for your interest.

  • Hello, see my comments below:

    1) VIN_MAX = 100mVp-p (TYP) with the condition THD = 1% means, as you described, that the output will distort further if > 100mVp-p input signal is applied (with the EC Table Global Conditions that GAIN = VDD, giving 40dB gain). However, this is the case for AGC disabled. If enabled, the amplifier will adjust the output level so as not to clip according to AGC parameters such as attack time, hold time, release time, and threshold.

    2) Regarding Figure 1, although the gain is not specified for that plot, it seems reasonable that 40dB was used, because that is the EC Table Global Condition, and based on the slew rate and amplitude of the left-most (clipped) output level. As you estimated, it appears that the input is ≈ 160mVp-p judging from the divisions of the oscilloscope's vertical scale. Looking at the clipped output level, the 1V/div vertical divisions, and where the sine wave is cut-off on the peak and trough, it appears that the amplitude would be 16Vp-p. This corroborates with the fact that the other gain options are 50dB and 60dB, which would result in ≈316X and 1000X gains.

    I hope this answers your inquiry. If not, let me know. Thank you for your interest.

  • Dear KTarrats,  Thank you for your quick answer!

  • Dear KTarrats,

    Thank your for your answer soon!

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