STM32H7 ADC low impedance input buffer

[Matt Blessinger]

I'm planning on using a STM32H750IBK6 to measure some high-speed analog signals. I will use the 2 direct channels to measure the signals as fast as possible. Per Table 183 of the datasheet max sampling rate is achieved when the analog external input resistance is less than 47 Ohms. My circuit comes from a higher impedance source than that, so I will need an opamp buffer to provide the low impedance source.

Is there an example buffer circuit or even part number that is advised to achieve <47 Ohm input impedance?

[Nikita91]

A high speed ADC requires a short settling time, therefore a high current.

Most OPAs have an output resistance of less than 47 Ohms, however 47 Ohms for 3.3V gives 70mA of current. This is a criterion to be taken into account.

[Matt Blessinger]

Thank you for the input. The datasheet lists a minimum sampling time of 74ns, which is ~13.6MHz, so I'm guessing I want an opamp that has bandwidth several times that. Plus unity gain stable and 70mA output capability.