Adjustable precision voltage source

Many applications require a precision voltage source which can be adjusted through zero to both positive and negative output voltage. An example is a bipolar power supply. Perhaps the most obvious implementation of a bipolar voltage source would be to use a bipolar voltage reference. However, a simpler solution is to use a single voltage reference and a precision unity-gain inverting amplifier. If a precision difference amplifier is used for the unity-gain inverting amplifier, the circuit requires just two chips and a potentiometer.