R_f provides negative feedback to control the gain. The gain depends on R_f and R₁.

Gain = 1 + R_f / R₁

 

The input resistance is equal to that of the op-amp. (Infinity for an ideal op-amp).

The non-inverting amplifier has a very high input resistance (impedance). This makes it ideal for amplifying small signal voltages from devices that can not provide any significant current. Such devices include capacitor microphones and piezo-electric sensors.