REVELTRONICS

Hi Artur, I've made my own Arduino-based circuits for stuff lately, one of them is a calibrator for my fuel gauge which in my car is very inaccurate. It sends a spoofed fuel sender signal to the gauge by PWM switching the fuel gauge circuit, based on my own ADC readings of the fuel senders (by using a voltage divider).

It works but I looked at my spare UTCOMP for inspiration, and I notice you use 10k resistors and an Op-Amp as a voltage follower before sending to the ADC pins of the AT90USB1286 microcontroller.

Given the AT90USB and the other microcontrollers by Atmel all have 100 megaohm input resistance, should I still use a resistor and op-amp like you do for my ADC inputs?

OAMP has 2 main functions, first of all it works like a buffer (voltage higher than 5V will not damage ADC input) and it also amplify signal (current consumption from source is near zero) so it will work with low impedance signals