XTR106: Maximum available gain

Hi Thorsten,

Thorsten Rink said:

Can you tell me what the minimum usable Value for Rg is   (maximum Gain).

It is determined by the transfer function below, see Iout and Vin. The min value of Rg is the max. output current, Io, where Io is typically 20mA (for 4-20mA current loop transmitter application). It is also a function of Vin signal.

If you have other questions, please let us know.  

Best,

Raymond

Thanks for reply,

I asked because  in figure 5 is a additional preamp for small signals.

So I think there is a limit to the usable gain in XTR106.

Regards 

Thorsten

Hi Thorsten,

The Figure 5 refers to max. current consumption that XTR106 is driving the input sensor + op amp/MCU etc., since XTR106 supplies all the current for the analog input front end, and the current loop transmitter has to be operated at 4mA without input signal. 

The XTR106's source current is limited to 3.4mA typical, may extend to 3.7mA, where 4mA is the maximum under no input signal requirements. In other words, ~3.7mA is the max. current limit for XTR106 to convert V-to-I linearly (lower will be optimum). And XTR106 has limited current source budget to drive the external sensing elements. Iret is the floating ground for the part, and this is two wire transmitter --> see the Iout transfer function marked in green box, when input signal is absent. 

If you have other questions, please let me know. 

Best,

Raymond