STM32 OpAmp Differential Strain Gauge Bridge Input

[Rob Ashworth]

Does anyone know if the PGA OpAmp in the STM32 has the ability to interface with a differential input - like a Strain Gauge Wheatstone bridge?  I'm not convinced its going to work because my signal is going to swing +/-50mV, and the OpAmp does no look like it can handle a differential input.  There's probably some jiggly pokery that can be done to condition it externally, just wondered if anyone has any experience before I go down that route myself.

[AScha.3]

See in rm opamp :

So you could add all circuit you need for biasing etc external and it should work as expected.

But use up 3 pins to get an opamp with some 3mV offset and about 1000nV/(sqrt Hz ) - no big player for low level signals. :)

For low level like Strain Gauge Wheatstone bridge i would add a typical chip for such use, like HX711:

24bit ADC , with bridge PGA input , about 50nV total noise (!) ->

+ about 2 $ investment...

[Rob Ashworth]

Thanks Ascha, I haven't come across that ADC before.  Looks good except too big for my application.

[MasterT]

If OPA's all 3 pins are accessible , than combine two OPA.

Circuits successfully implemented in one of my projects with nucleo-G474re.

*resistors 10k - internal PGA matrix.

[Rob Ashworth]

Ah ok, so I could do it, except I have the problem that I have 2 sensors, so would need 4 op-amps.  The G4 that handles this is too large, so looks like I'm back to using and external ADC.  Will probably go for something like the ADS1292.  Build in PGA and differential inputs.  Hoping ST bring out a controller with an Instrumentation AMP that can handle Differential signals some time soon.

[MasterT]

If G4 is too large, than ads1292 is small? Have you compare footprint?

BTW, STM has stm32f373 IIRC, with SD adc.