Analog Output Connections

The following figure shows the PXIe-4468 analog output circuitry block diagram. Depending on the connector type, connect the signals as shown in the inset.

The PXIe-4468 output stage is a differential amplifier. The output stage can be configured to pseudodifferential mode in software, where the AO- terminal is internally connected to chassis ground through a 50 Ω resistor. This connection introduces a gain difference in the output stage of -22.0 mdB, for which the software corrects automatically. Refer to the NI-DAQmx Help for more information about terminal configuration.

The PXIe-4468 output stage can also be configured to pseudodifferential mode by making an external connection between AOn+ or AOn- to chassis ground. This connection introduces a gain change in the output stage of -22.0 mdB, for which the software does not correct.

For most applications, configuring the PXIe-4468 output stage in differential mode will yield the best performance. For improved common-mode noise rejection, it is highly recommended to make a connection between the chassis ground of the PXIe-4468 and the input device ground. This connection is critical when the input device is isolated; if this connection is not available, it may be better to configure the PXIe-4468 output stage in pseudodifferential mode.

The following figure show the recommended output connection.