Table Of Contents

PXIe-5433 Analog Output Path

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    Last Modified: January 19, 2018

    The two-channel PXIe-5433 supports independent-channel waveform generation.

    The following processes outline the generation of analog waveforms with the PXIe-5433:

    1. The 16-bit digital waveform data from the Waveform Generation Engine is passed through fractional resampling and filtering.
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      Note  

      When the PXIe-5433 is configured to standard function output mode, the signal bypasses fractional resampling and filtering.

      You can enable or disable digital filtering using niFgen Configure Digital Filter, niFgen_EnableDigitalFilter, or niFgen_DisableDigitalFilter. By default, the digital filter is enabled.

    2. The signal passes through a digital gain circuit.

      Digital gain multiplies waveform data by a factor you specify with the Digital Gain property or the NIFGEN_ATTR_DIGITAL_GAIN attribute before converting the data to an analog signal in the DAC.

      Digital gain can be changed during waveform generation without the glitches caused by switching that are common when changing analog gain. However, the output resolution of the DAC is a function of digital gain, meaning that only analog gain makes full use of the resolution of the DAC.

    3. The signal passes through the 800 MS/s DAC.
    4. The signal passes through fine preamplifier attenuation: a set of selectable solid-state attenuators that provide 0 dB to 2.4 dB of signal attenuation in sixteen 0.16 dB increments. The final 0.16 dB increment uses DAC-code scaling to configure the exact amplitude based on the gain setting.
    5. The signal passes through a DC offset amplifier that adds the specified DC offset voltage.

      You can adjust the amount of DC offset added to the signal, up to one-half of the value of the gain setting, by using either the Arbitrary Waveform Offset property or DC Offset property, or the NIFGEN_ATTR_ARB_OFFSET or NIFGEN_ATTR_FUNC_DC_OFFSET attributes.

    6. The signal passes through an enabled 80 MHz time-domain, Bessel analog filter. The enabled analog filter increases the delay from the time at which the PXIe-5433 receives a trigger to the time at which the analog output signal is generated.
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      Note  

      When the PXIe-5433 is configured for sine wave generation in standard function output mode, the signal bypasses the time-domain, Bessel filter.

    7. The signal passes through medium-range preamplifier attenuation: a set of selectable solid-state attenuators that provide 0 dB to 10.23 dB of attenuation in five 2.56 dB increments.

      You can adjust the amount of attenuation by configuring the Arbitrary Waveform Gain property or Amplitude property, or the NIFGEN_ATTR_ARB_GAIN or NIFGEN_ATTR_FUNC_AMPLITUDE attributes. NI-FGEN calculates and sets the correct amount of attenuation required, corresponding to the gain setting.

    8. The signal continues through either the low-gain amplifier path or high-gain amplifier path.
      • The low-gain amplifier path is used for waveforms that have all output voltages equal to or less than ±2.75 V into 50 Ω loads. The low-gain amplifier has a fixed gain.
      • The high-gain amplifier path is used for waveform output voltages greater than ±2.75 V into 50 Ω loads. The high-gain amplifier has a fixed gain and enables maximum peak-to-peak signal amplitude (Vpk-pk).

      By default, NI-FGEN automatically selects the amplifier path the signal passes through based on the gain or amplitude setting.

      Maximum Gain (Vpk-center) Maximum Amplitude (Vpk-pk)
      50 Ω load impedance 6 12
      1 MΩ load impedance 12 24

      Alternatively, you can use the Analog Path property or the NIFGEN_ATTR_ANALOG_PATH attribute to set the signal path to remain constant regardless of the gain setting for applications requiring only one of the amplifier paths. Configuring a constant signal path through the low-gain amplifier path regardless of the gain setting affects the maximum output value allowable for that particular gain setting: The maximum gain setting for signals configured to use the low-gain amplifier path is 2.75.

    9. The signal passes through coarse postamplifier attenuation: a set of two passive attenuators that provide 0 dB to 38.37 dB of attenuation in four 12.79 dB increments.

      You can adjust the amount of attenuation by configuring either the Arbitrary Waveform Gain property or Amplitude property, or the NIFGEN_ATTR_ARB_GAIN attribute or NIFGEN_ATTR_FUNC_AMPLITUDE attribute. NI-FGEN calculates and sets the correct amount of attenuation required, corresponding to the gain or amplitude settings.

      At this point, the signal has an applied maximum attenuation of 51 dB. After this point, the signal will continue to digitally attenuate.

    10. The signal passes through the output enable relay.
      • When the relay is disabled, ground is connected to the output through a 50 Ω resistor. Waveform generation continues while the output enable relay is disabled.
      • When the relay is enabled, the analog waveform is generated at the analog output connector.

      You can enable or disable analog output using niFgen Output Enable or niFgen_ConfigureOutputEnabled.

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    Note  

    When you change a setting that results in a relay switch, the bouncing of electromechanical relays on the PXIe-5433 distorts the output signal for about 10 ms.


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