Hi Friends,
Often we need voltage supplies other than +5V or +3.3V in circuits. The components on board requiring such odd supplies are usually very few in number and are usually.
i. Op-Amps / In-Amps.
ii. ADC / DAC.
iii. V-F / F-V Covnerters.
etc.

In order to supply these odd voltages there are several methods.
i. Having a separate supply module on supply card specifically to supply these devices.
ii. Using a DC-DC converter space saving but expensive I remember recently I got quotation for +5V to +12/-12 DC-DC covnerter from RS components and I was surprised to see price tag of Rs. 1100 - Rs. 1300 ie. approx. 28 USD.
iii. Using MAX232/MAX202 etc to get a small current.

The MAX232 technique was discussed here a few days back.

Let's have a WEOT discussion on methods of fetching such odd voltages.

Regards,
Prahlad Purohit