How can I invert this current control?
You can use a PNP transistor instead:







simulate this circuit &ndash; Schematic created using CircuitLab

Note that the LED supply voltage cannot be more than about 2 V higher than the maximum voltage of the DAQ output. With any higher voltage, the LED will not be completely dark when the DAQ is at its maximum voltage.

Note also that this requires the DAQ to sink current from the base of the transistor. This current will be a small fraction of the LED current &mdash; with a maximum LED current of about 20 mA, the base current will be on the order of 20-40 &micro;A.