Build A Negative Voltage Generator
Everyone needs a negative voltage rail eventually, but most only have a single rail supply. This article will show you how to build a negative voltage generator that runs off a single rail supply.
Many hobbyists may have come across an op-amp circuit that uses a dual rail supply. In order to provide the dual rails power, two power supplies can be used but many do not have access to such equipment thus two individual power supplies may not be ideal. One solution is to split the incoming power supply and create a virtual ground between two resistors in a potential divider.
However, this solution has some trouble. Firstly, the current sinking/sourcing capability of the virtual ground is limited. Secondly, the supply voltage has been divided by 2 (for example, a 9V battery could become ±4.5V but 4.5V is the maximum achievable voltage).
But using an oscillator, some diodes, and a clever arrangement of capacitors, we can exploit an effect called capacitive coupling whereby a negative voltage near equal to the supply voltage can be generated from a single rail supply.