NI 5402/5406
Analog Output

The following figure shows the NI 5402/5406 Analog Output signal path.

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NI 5402/5406 Analog waveforms are generated as follows:

1. The digital waveform data from the Standard Function Generation Engine is passed to a digital gain circuit and then high-speed DAC. This DAC also implements a portion of the output signal path attenuation with a range of 0 dB to 3 dB. Refer to the module specifications for the exact resolution. You can adjust the amount of attenuation by configuring the Amplitude property or the NIFGEN_ATTR_FUNC_AMPLITUDE attribute. NI-FGEN calculates and sets the correct amount of attenuation required, corresponding to the gain setting.
2. Following the DAC, the signal then passes through a switchable lowpass Analog Filter to remove Aliased Images. For User-defined waveforms created in Standard Function mode or Frequency List mode, you can select whether to include the Analog Filter in the Analog Output path using either the niFgen Configure Analog Filter VI or the niFgen_EnableAnalogFilter and niFgen_DisableAnalogFilter functions.
3. Either the Main path output or the Square Wave Output path is selected based on the desired waveform which then passes through the DC Offset Amplifier that adds the desired DC offset voltage. For User-defined waveform created in Standard Function mode or Frequency List mode, you can adjust the amount of DC offset added to the signal up to ±5 V_pk including AC and DC components into 50 Ω impedance. Refer to the DC Offset property, or the NIFGEN_ATTR_FUNC_DC_OFFSET attribute for more information.
4. The signal then passes through the Pre-Amp Attenuation section, a set of selectable solid-state attenuators that provide 0 dB to 12 dB of attenuation in 3 dB increments. You can adjust the amount of attenuation by adjusting the Amplitude property, or the NIFGEN_ATTR_FUNC_AMPLITUDE attribute. NI-FGEN calculates and sets the correct amount of attenuation required, corresponding to the gain setting. Refer to the Amplitude property, or the NIFGEN_ATTR_FUNC_AMPLITUDE attribute for more information.
5. Following the Pre-Amp Attenuation section, the signal can take one of two paths: the High-Gain or Low-Gain Amplifier path. NI-FGEN automatically selects the best amplifier path between the High-Gain and Low-Gain amplifiers by default based on the Amplitude property or the NIFGEN_ATTR_FUNC_AMPLITUDE attribute setting. Alternatively, you can set the signal path to remain constant regardless of the amplitude setting for applications requiring one path or the other. Refer to the Analog Path property or the NIFGEN_ATTR_ANALOG_PATH attribute for more information.
   1. The High-Gain Amplifier path is used for waveform output voltages greater than ±1.0 V (±0.83 V for sine waveforms) into 50 Ω. The amplifier has a fixed gain and is included in the signal path to enable the signal generator to provide the maximum V_pk-pk.
   2. The Low-Gain Amplifier path is used for waveforms that have all output voltages equal to or smaller than ±1.0 V (±0.83 V for sine waveforms) into 50 Ω. The amplifier has a fixed gain.
6. The signal passes through the Post Amp Attenuation section, a set of two passive attenuators 12 dB and 24 dB. You can adjust the amount of attenuation by configuring the Amplitude property or the NIFGEN_ATTR_FUNC_AMPLITUDE attribute. NI-FGEN calculates and sets the correct amount of attenuation required, corresponding to the gain setting.
7. The signal then passes through the Output Enable relay. When the Output Enable relay is disabled, ground is connected to the output through a 50 Ω or a 75 Ω resistor. Intentionally, Standard Function Generation continues while the output enable relay is disabled. When the relay is enabled, the analog waveform is seen at the CH 0 connector. You can enable or disable the output of the analog waveform generator. Refer to the niFgen Output Enable VI or the niFgen_ConfigureOutputEnabled function for more information.
8. The signal then passes through a 50 Ω/75 Ω selector to the CH 0 connector. You can configure the output impedance of the analog waveform generator, refer to the niFgen Configure Output Impedance VI or the niFgen_ConfigureOutputImpedance function.

Note  The NI 5402/5406 uses mechanical relays to switch between the optional sections in the Analog Out path. When you change a setting that results in a relay to switch, the bouncing of electromechanical relays on the NI 5402/5406 distorts the output signal for about 10 ms.