Getting a USB DAQ Device to Output a Higher Voltage or Current

Updated Jul 30, 2018

Reported In

Hardware

  • USB-6501

Driver

  • NI-DAQmx

Issue Details

My external device needs 5V minimum voltage and my USB DAQ Device supply voltage is often below 5V, I know this is the expected output but how can I increase this and the current to allow connection to my low impedance circuit?

Solution

A way of having more control over the voltage and current is Using a Unity Gain Buffer (Voltage Follower) with a DAQ Device and the load as picture below; this allows the load circuit to be powered externally so there are no current/voltage limitations implied by the DAQ device.

Additional Information

The USB ports provide the signal for the device, the signal generally varies from one manufacturer to another but the valid range is from 4.4-5.25 VDC.
 
A voltage follower transfer’s voltage from a high impedance circuit to a low impedance level circuit, the low impedance circuit is prevented from loading the 1st circuit. This is done without drawing current from the initial circuit, but allows varying currents to output from the operational amplifier, dependent on the operational amplifier properties. This will also allow the target circuit to receive more current then the USB device produces.

 

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