Is there a reason I can't use the DAC and op amp on STM32L476 to generate a 4 to 20 mA current loop?

[LFerg.2]

Generally, a basic circuit design to generate a 4 to 20 milliamp current loop would use an op amp, FET and handful of resistors in addition to an input voltage or current which, in this case, would be the DAC. (please see attached) Can the internal op amp on the STM32L476 be used in this instance?

[Uwe Bonnes]

With R7 in the 20... 100 Ohm range, I think this will work.

[Peter BENSCH]

Well, it looks like the circuit you put in is from here, doesn't it?

The operational amplifier used there provides an offset voltage of 10µV, while the internal operational amplifier of the STM32L476 is specified with 3 mV over the temperature range. Why not configure it in mode Standalone and give it a try if the spec is fine with you.

However, there is also an external opamp with an even better offset from STMicroelectronics: the TSZ121/122/124

Good luck!

When your question is answered, please close this topic by choosing Select as Best. This will help other users find that answer faster.

/Peter

[LFerg.2]

Thank-you!