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XTR110 - Output Load Resistance

Fabio Silva
Prodigy 20 points
Other Parts Discussed in Thread: XTR110, XTR111

Hello everyone! 

I want to buy this device XTR110 to build a Voltage to Current Converter.

I already have the Voltage range from 0V to 5V that will be used as Input. (in fact, I tried to convert this voltage in current by using a simple BJT NPN Transistor as a current source controlled by voltage, but it didn't work as expected).
In the Output, I'm using a PLC to receive and read the 4-20mA signal, but the idea of my project is use other receivers with Resistance from 100 until 500 Ohms, and the current should be stable. 

The datasheet of XTR110 specifies a typical RL of 250 Ohms in output (Figure 1). My question is: if use a power supply about 20V and use a device in the output with load resistance until 500 Ohms, the output current will be the same? 

Thank's! 

  • 0
    TI__Guru 62825 points

    Hello Fabio,

    The XTR110 is a good product for this application and has been a popular product for a long time.  Also consider the XTR111 which is a newer and more accurate / cost effective option.

    Regarding your question, as long as you don't violate the maximum load resistance vs. power supply voltage shown in the figure below the output current will not change by a noticeable amount as the load resistance changes.

  • 0 in reply to Collin Wells
    TI__Guru 62825 points

    Hi Fabio,

    It's not important when using the XTR110 / XTR111 but I forgot to comment on your BJT implementation issues. Keep in mind that a BJT is effectively a current-controlled current source and using a voltage to control the output current is not the best option. MOSFET devices are effectively voltage-controlled current sources and would make a better option for a direct V-to-I circuit.

  • 0 in reply to Collin Wells
    Prodigy 20 points

    Ok, Collin!

    You are fast! I really appreciate your time and your explanation. 
    I'm trying XTR11x as soon as possible. I'll prefer XTR110 for now, because of the DIP16 package. Besides, I believe it is enough to attend the project specifications. 

    Thank you once again.

    Regards

    Fabio Silva