Dear All,
I would like to get some advise on analog circuit for signal measurement.
My circuit is quite simple, I have two op-amp for amplification in a non-inverting circuit and then go into a 12bit A/D. The first op-amp is a low-offset and second one adjustable gain.
The fact is this circuit needs to be as stable as possible as absolute measurement will be done with it. The accuracy shall be below 0.2%. As the system has a "software" calibration, the important part is that it stays stable over the time.
The noise is also a concern, based on some publications, it is recommended for the op-amp resistor circuit two be as low as possible, in my case 10ohm and 200ohm (20x amplification).
But now I'm doing some tests and there is an other concern, as the resistors are low, the influence of the soldering resistance will have higher impact.
As for example, if the soldering resistance is 0.05ohm, on a 10ohm resistor it represents 0.5% but will only represents 0.005% on a 1kohm.
The problem is with thermal stress and ageing, the soldering resistance is likely to vary and comprise the stability.
All the circuit is SMD with 0603 resistors.
Anybody has experience with this, and is the thinking correct ?
Thanks
I would like to get some advise on analog circuit for signal measurement.
My circuit is quite simple, I have two op-amp for amplification in a non-inverting circuit and then go into a 12bit A/D. The first op-amp is a low-offset and second one adjustable gain.
The fact is this circuit needs to be as stable as possible as absolute measurement will be done with it. The accuracy shall be below 0.2%. As the system has a "software" calibration, the important part is that it stays stable over the time.
The noise is also a concern, based on some publications, it is recommended for the op-amp resistor circuit two be as low as possible, in my case 10ohm and 200ohm (20x amplification).
But now I'm doing some tests and there is an other concern, as the resistors are low, the influence of the soldering resistance will have higher impact.
As for example, if the soldering resistance is 0.05ohm, on a 10ohm resistor it represents 0.5% but will only represents 0.005% on a 1kohm.
The problem is with thermal stress and ageing, the soldering resistance is likely to vary and comprise the stability.
All the circuit is SMD with 0603 resistors.
Anybody has experience with this, and is the thinking correct ?
Thanks