ADS4125: current monitor solution

Forwarding to the amplifier group to advise.

Hello, 

Could you provide more detail on what the various blocks represent in the diagram. Also what is the bandwidth required for the measurement? Typically we would implement this type of circuit using a current sense resistor and amplifier to measure the voltage across the resistor. 

Best, 

Jacob 

that is the leakage current measure, 15hz ~1MHZ

did you have any advise, AMP have 0.1~256 gain? 

Hi Alex, 

Are you requesting that the part have a variable gain control between 0.1 and 256 V/V gain? Also, what power supply voltages do you have available and what is the common mode voltage where you are trying to measure the current? 

Thanks, 

Jacob 

I have *0.1~ *256 GAIN requirements and the bandwidth needs DC, 15~1MHz, and the output voltage is 0~8V.

HI Alex, 

My apologies for the delay on this thread. Due to the speed range of this application I will send it over to our precision amplifier Team. 

Hi Alex,

Chen Alex1 said:

I have *0.1~ *256 GAIN requirements and the bandwidth needs DC, 15~1MHz, and the output voltage is 0~8V.

It is difficult to meet all the above requirements in a single instrumentation amplifier. Below is our PGA selection. 

https://www.ti.com/amplifier-circuit/pga-vga/products.html#3229=PGA&sort=511;asc&

For instance, the selectable gain from 0.1 to 256V/V (below 1 V/V) instrumentation amplifier are typically associated with PGAXXX part number, such as PGA280, PGA281, PGA855 etc.. 

Your other requirements are up to 1MHz and output swing up to 8Vdc, which are high voltage instrumentation amplifier. 

I do not see that one single instrumentation amplifier is able to meet all the above requirements. PGA855 meets some of your requirements, but gains are only scaled up to 16V/V. You may have to adapt dual stage to implement the application. 

If you have other questions, please let me know. 

Best,

Raymond