But Prahlad....Kai was suggesting that you throw the 1N4007 or 1N4004 type diodes away. These things have very high forward voltage drops even at relatively low currents. If instead you used Schottky diodes such as BAT54 type you can see an increase in performance of the ICL7660 circuit. The lower voltage drop of the Schottky diode translates to an increrase in output voltage.
Michael Karas