A Non-inverting amplifier increases the amplitude of a signal. Its input resistance is that of the op amp itself (infinite in an ideal op amp), which makes it perfect for amplifying small signals, that can provide very little current on their own.

One thing to note quickly. The output can never be higher than the positive supply voltage, or lower than the negative supply voltage.

Non-inverting amplifiers however, can only provide a minimum gain of one. This means the output will always be at least the same value as the voltage on Vin. Its gain can be calculated by using the following formula: