INA333: DC Amplification using INA 333

Hi Hari,

as the input offset voltage of INA333 is up to 25µV and the input offset voltage drift is up to 0.1µV/°C it will be difficult to accurately measure a 1µV DC signal. But, of course, the chip can amplifiy such a small DC signal.

Kai

Hi Kai,
Good day...
Could you please suggest some other IC's which will help to measure 1uA precisely.
Regards
Hari

Hi Marek,
I want to amlify 1uV .For current measurement purpose.
Regards
Hari

Hi Hari,

and what currents do you want to measure?

Do you want to use a shunt resistance to generate a voltage drop? Or do you want to use a TIA concept, like Marek mentioned?

Kai

Hi Kai,

I need to generate voltage on a shunt resistor and need to amplify the same

Regards

Hari

Hari, would you please so kind and tell us what shunt resistor you want to use? :-) It's impossible to help without any data...

Kai

Hi Kai,

I am attaching the initial block diagram along with this mail

Shunt resistor is not calculated yet.

if you don't mind please go through this block diagram.

Expecting your valuable suggestions on shunt resistor Design according to the requirement given in the Block diagram

Regards

Hari

Hari,

This is not much of a specification. You have posted in multiple locations with different ranges given for the current you are measuring. Given that you have not selected a shunt, please confirm the range of current that you need to measure and with what resolution. What is the resolution of your ADC and what will be the full scale range of this converter (to determine LSB size)? Based on above I am assuming that you are using a 1.2V LDO. As Kai and Marek have mentioned the dc errors of the INA333 and any other device you could use here are going to dominate your low signal levels and will thus require calibration. You may be better of using a zero-drift op amp configured as a difference amp to at least avoid the need for a temperature calibration.

Hi Zak,
We are in a design phase final values are not decided yet. Most probably current is from 1uA to 100ma.
Regards
Hari

Hi Hari,

Please understand that without having a defined system it is very difficult for us to make recommendations. Generally, you will choose the uC and the ADC first and then design the front end amplifier. You will need to switch in different shunt resistors to maintain reasonable accuracy across the entire range. The values you should use depend on your system specifications, such as how much resolution you need, what kind of SNR you are targeting, the full scale input range of your converter, etc. You will need to use switches that have very low leakage and low on resistance to ensure the switches do not significantly impact your measurement. Relays are ideal, but you may be able to find a FET that will be suitable and can be driven from a GPIO pin on your micro once the ADC registers that a measurement is out of range.