AD8476 output oscillation

Hi,

I have a simple circuit (shown below) which I'm currently testing. The output of this amplifier is directly connected to an ADC.

The test consists of short-circuiting both inputs and connecting them to a waveform generator at 1.65 V DC. I would expect a differential output voltage of 0V; however, when I measure with the oscilloscope, I notice a 4 MHz oscillation on both output channels that I don't fully understand.

This oscillation is present even if I drive the amplifier with differential sine wave (inputs not shorted). The only case in which the oscillation dissapears is when I ground both inputs.

Do you have an idea of the possible problem?

Thanks,