# How should I choose the resistors in a voltage divider?

I would like to measure tree signals by using a ucontroller.

the signals are between

• -5V to 5V
• 0V to 2V
• -20V to 20V

The frequency of the signals are between 1MHz and 5MHz. The ADC range is between 0 and 3V.

I built the following simulation, where I am dividing and shifting the measured signal:

I have the following questions regarding the circuit:

• How should I choose the resistors in the voltage divider and OP-AMP gain?
• How can I make 'dynamic' voltage divider? I mean controlled by microcontroller? I checked the analog switches in the TI website but I am not really familiar with those switches.
• How can I protect the circuit from over voltages?

• Finally, the resistors should be of sufficient power rating to tolerate the power dissipation P = I^2 x R for the current drawn through them, I = V(DC1) / (R1 + R2)