Z-Diodes are often used for simple voltage stabilized circuits. It is very important to use the Z-diode with the correct parameters.
This article shows an example for the voltage characteristics of two Z-diodes.
This article takes a look on the costs of batteries compared to accumulators and additional chargers.
This article shows an operational amplifier (OP) that is used as an impedance converter. This ciruit will then extended to a non-inverting amplifier.
What hobbyist does not know the problem, that a commercial case does not quiet fit for the current project?
This method shows a case construction with a low bill of materials.
In some cases one needs a comparator with a hysteresis. This curcuit suggestion shows further the possibility of a inverting or non-inverting operation.