the non-inverting amplifier
In the non-inverting amplifier the signal goes straight into the plus input, which draws essentially no current, while a resistor divider from the output back to the minus input sets the gain. The output is a same-polarity, scaled-up copy of the input, and the circuit barely loads the source.
Its gain is 1 plus Rf over Rg. Derivation by the virtual short: V- equals Vin. The minus node sits at the tap of a divider made of Rf (from output to the minus node) and Rg (from the minus node to ground), so V- equals Vout times Rg over (Rf plus Rg). Setting that equal to Vin gives Vout equals Vin times (1 plus Rf over Rg). With Rf of 90 kilohm and Rg of 10 kilohm the gain is 10. Note the minimum gain is exactly 1, reached when Rf is 0 or Rg is infinite.
The big advantage over the inverting amplifier is input resistance: the plus input draws almost no current, so the circuit presents a very high impedance and hardly disturbs a delicate source like a sensor. The trade-off is that the gain can never be less than 1, so you cannot use this topology to attenuate, and the input voltage swings with the signal (high common-mode), which can matter near the rails.
Choose Rf of 19 kilohm and Rg of 1 kilohm, giving a gain of 1 plus 19 equals 20. A 0.1 V sensor signal becomes a clean 2 V, in phase, while the sensor barely supplies any current.
High input impedance makes this the natural choice for buffering high-impedance sensors.
Gain can never drop below 1 here, so it cannot attenuate. Also the input sees the full signal as common-mode voltage, unlike the inverting amp's quiet virtual ground.