I have a PLL that needs -9v I need to use 9V batteries. I can use it with split supply but that means 0nly 4.5V it needs 5V min. Its for a reciever so the gain is important. With opamps At 4.5V ill wont really have much room for battery degradation, a 9v battery will easily read only 8V or so within a week of use!!!
I ordered a (free sample!!) of a MAX1440 switchd cap voltage inverter will invert +9v to -9v supply , around 95% efficient, ive never used one but I hope it can do the job!
thanks