Achieving 0.000005% Resistor Matching for 24-bit R-2R DAC: Wheatstone Bridge or Alternatives

Hi,

I am looking to match resistors with a very high degree of accuracy/tolerance.

One can purchase 0.01% resistors quite easily, but with regards to a project such as an R-2R ladder DAC, which has 24bit depth, then the accuracy/tolerance would have to be 0.000005%.

Since such a tolerance is not available, then the next option is to match resistors using a Wheatstone bridge.

What i am not sure of is whether it is possible to achieve the matching to such tolerance, or if there is another method of achieving the accuracy such as paralleling the resistors (0.01% + trim) to match the target resistance. This would require a fair amount of physical testing to trim the resistor to match the selected target.

Is this method doomed to fail, or are there better alternative methods ?

Thanks and regards,

Richard.

Try to use delta-sigma DAC.. I am a bit wondering if the wheatstone bridge really match to 0.01% with a meter. The R-2R ladder is suppose to not need high precision resistors.

Hi Kevin,

Thanks for the reply.

This is a project - others have implemented the same - but not with the accuracy required.

The reason for using a Wheatstone Bridge is that once in balance it is very sensitive to variation.

This is the issue - i would need to know how to set up the bridge and use for matching resistances - trimming etc., to the accuracy required. It may be that the imbalance causing the current through the galvanometer is too low for the accuracy required.

I am unsure as to the details and what is actually possible - so was asking to see if anyone with experience can provide guidance.

Thanks and regards,

Richard.