Q:

How to use one 12V power supply to supply two Op/amp with 5V and 12V voltage supply?

I am trying to design a circuit and i have two Op-Amp with different supply voltage with -+12V for LT1220 and +-5V for LT1193. i want to use just one power supply with +-12V. in that case for Lt1193 i would like to make a local power supply for that. using Zener diode with zener voltage regulator is good approach or is there any high efficient way in practice for this purpose?

A:

Depending on your current requirements you basically have two approaches:
low currents just use a linear regulator, something like the (somewhat) good, (definitely) old 7805. A linear regulator dissipates a lot of power, the current through it being constant. For a 7V drop at 100mA you get 700mW, it is not a lot but it can be too much. I guess your current needs are much lower, so a linear regulator might suit you.
high currents you can use a monolithic DCDC step down regulator to get some 6V from your 12V, then use an LDO (Low Drop Out) regulator to get to 5V, nice and smooth. You need the LDO because usually the output voltage of a DCDC regulator is quite messy and noisy, something you normally cannot accept in an opamp circuit.
The second solution is actually the best in almost any case, unless your current requirements are very low (less than 100mA let's say), but your BOM gets bigger and more costly. If you need low currents the linear only solution is the best, mainly because you only need one chip and a couple of capacitors.
If you opt for the linear path please search a suitable part for your application, don't just throw in a 7805, there are cheaper and better solutions on the market.

