Figure 6.2 shows a non-inverting amplifier, sometimes referred to as a voltage follower.
Figure 6.2: Non-inverting, unity-gain amplifier.
Applying our rules to this circuit we have
The amplifier gives a unit closed-loop gain, , and does not change the sign of the input signal (no phase change).
This configuration is often used to buffer the input to an amplifier since the input resistance is high, there is unit gain and no inversion. The buffer amplifier is also used to isolate a signal source from a load.
Often a feedback resistor is used as shown in figure 6.3.
Figure 6.3: Non-inverting amplifier with feedback.
For this circuit
The gain is