One of the newer features in Signal Chain Designer is the DC Error view which allows you to see offset and gain error contributions from all the components in a signal chain design over a specified temperature and input range. In the example below, you can see that for a specified -40°C to 85°C temperature range, the ADC dominates gain error, and the second amplifier dominates offset error.
Signal Chain DC Error View (Adjust Settings in the Red Box)
To get started, specify the ambient temperature range and then open the advanced settings options on the next line (click the blue gear button). This will let you select how you want the errors referred, how to combine errors (RSS or Linear), and whether you are performing a one- or two-point calibration. You can also specify the calibration temperature and how much uncertainty you expect. Clicking the blue “?” help icons will give you more details to help decide the best option for your design.
Advanced DC Error Settings
You can also click into the individual components of the signal chain to better understand where the error contributions are coming from and optimize the design if required. For example, you could choose an amplifier with lower offset or even change the tolerances and temperature coefficients of resistors contributing to gain error and gain drift respectively.
DC Error Summary View for an Amplifier Gain Stage
To change the resistor tolerances and temperature coefficients, click on the % next to the resistors.
Changing Resistor Specifications
There are two other tabs for the DC Error view for the individual components. The “Total Error Plot” tab shows the offset error in dark blue and the gain error contribution vs input voltage in light blue as shown below.
Total Error Plot View (Amplifier 1 from Example)
The “All Errors Table” tab, shows all the component specifications and their respective sensitivities contributing to overall error. The help button next to Ambient Temperature Range will explain how the drift sensitivity is calculated. If the specification isn’t in the datasheet for the product, you’ll see an orange warning (bias and offset current drift below). Clicking on the warning will explain how we determine a coarse estimate for the spec.
All Errors Table View (Amplifier 2 from Example)
Check out the DC Error Simulation training video to see another example using this feature to learn more.
If you have any questions on this topic or the Signal Chain Design tool, please ask in our Engineer Zone forum.