Say I need to create a negative supply rail of -5V (+-0.5V) from a DC input of +5V without the use of any ICs whatsoever. The components available to me are BJTs, Mosfets, diodes, resistors and caps. So far my basic understanding is this -
Make an oscillator circuit (maybe astable multivibrator) to convert the positive DC into a 0-5V square wave and then use a voltage doubler to get a DC voltage on the negative side.
The problem is that my output is at around -3.5V. Maybe I should amplify the square wave before passing it to the next stage? Or ditch this method altogether? Suggestions would be appreciated.