https://www.mikrocontroller.net/articles/Operationsverst%C3%A4rker-Grundschaltungen
Easy way to generate a reference voltage. There is a normal stabilization circuit with a Zener diode used, but no longer has the bad characteristics of the standard circuit with only resistor and Zener diode. With a Zener diode, the exact voltage depends on what current flows through it. However, this current (and thus also the level of the Zener voltage) would change if a consumer would load the Zener diode directly with its current flow. As a result, the voltage level of the Zener diode would vary slightly depending on the consumer. The voltage follower prevents this because it now provides the power needed by the consumer.
