Wish to measure three small voltages (<1V) on a 16f676. Set Vref to 1.023V, but found the reading fluctutes with an injected voltage of 100mV on AN1. Checked AN1 ok with internal vref. This raises two questions:

1. What is the lowest practical value of Vref for the ADC to work correctly?

2. Does Vref require a buffer or filter capacitor - Checked with scope and Vref looked smooth?

Thanks