Build Your Own Negative Voltage Generator

Many hobbyists will 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 or the design needs to be portable and 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 issues. Firstly, the current sinking / sourcing capability of the virtual ground is limited and, 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!”