Voltage inverter using 74HC14 HCMOS circuit

Using a 74HC14 HCMOS circuit and some electronic components can be built a very simple voltage inverter electronic project. Using this circuit diagram ca be obtained a negative voltage from a positive voltage.
The output signal is converted by a charge pump, to a negative supply voltage. Diodes used for this purpose are Schottky type which, due to their low threshold voltage, does not reduce load voltage level as much as silicon diodes.
In no-load, output voltage is about 6 V, and when load is about 1 mA, output voltage drops to 4 V If the voltage drop is allowed below (up to half the supply voltage) can obtained a 10 mA current. Can not get a higher current load or a lower voltage drop by increasing the output capacitor charge pump, because the circuit fails.