Gain is 10 for modified current monitor circuit?

[treez]

Hello,
Please could you confirm that gain = 10 for a MAX4173T with a 12k resistor added from its output to ground ? (the gain is 20 without this resistor being added)

Page 7 of the datasheet details the relevant calculation...

MAX4173T datasheet
https://datasheets.maximintegrated.com/en/ds/MAX4173-MAX4173T.pdf

 

[KlausST]

Hi,

usually gain is 20. With high impedance load.

I see your point... because of the internal 12k....But on page6 it says approximaltely 12k... this tells me not to rely on that.

In the other thread you use a 0.1 Ohms shunt. Maybe use a 0.05 Ohms shunt instead.

Klaus

Klaus

 

[treez]

in page 3 it just says "12k", suggesting that 12k is very accurate, I see where you saw "approximately 12k" but that might be taking into account the output impedance of the current mirror aswell?

I need a lower gain, otherwise at our lower end of the current range, the sense voltage will get ridiculously small.

 

[KlausST]

Hi,

usually the current monitor ICs are calibrated for good CMRR and gain precision.
Output impedance may not be calibrated.

I also don´t think that the current mirror should change the output impedance significally.
It would decrease overall performance.
A (good) current mirror has about infinite impedance.

Klaus