MSP430FR2355: EXP430FR2355 - Strange behavior at some opamp gains

Part Number:MSP430FR2355

Hi,

I received one launchpad exp430fr2355 and did some tests based on the out of box demo.

I connected an Analog Discovery on pin P3.5 to measure the signal of DAC and pin P1.5 to measure the signal at the opamp output, but I noted some strange behavior.

Using the non-inverting configuration of opamp the gain 2x and 3x show a huge noise when connected to oscilloscope tip configured to 1x mode.

But if I activate the attenuator (10x mode), everything works well.

The same thing happens in the inverting configuration, but with the gain 1x and 2x.

Note that from on other gains it works very well.

Does somebody have an idea what's happening?

Thanks.