# +12V and -12V for supplying Op-Amps in my circuit

What is the easiest and cheapest method for acquiring +12V and -12V for supplying LM358 Op-Amps? In my school's laboratory we are using Agilent voltage supply but that kind of supplies are really expensive for me. What is the easiest and safest method to obtain these values? PS: I've tried using 2x9V and 4x1.5V batteries in series with a voltage divider. And making the ground of my circuit their mid point. It was useful until I was dealing with AC signals. All my signals are distorted because of it. I've searched for voltage regulators found +12V voltage regulator circuit from 24V however I can not figure out how to obtain -12V at the same time. Thank you for your kind helps.

• "... but that kind of supplies are really expensive for me." Well, yes, you did say "Agilent". Try something from Rigol instead. Commented May 8, 2016 at 1:06
• Bench supplies are the cheapest piece of the test equipment chain. Commented May 8, 2016 at 1:20
• ibsrt.com/imgitem/… This link may help. You could obviously use a different BJT like a 2N3904. Commented May 8, 2016 at 1:26
• Duplicate of this? electronics.stackexchange.com/questions/187029/… Commented May 8, 2016 at 2:18

I've tried using 2x9V and 4x1.5V batteries in series with a voltage divider.

You don't need a voltage divider. Just connect 4 sets of 4x1.5V cells in series and make their midpoint the ground, like this:-

simulate this circuit – Schematic created using CircuitLab

When connecting batteries in series always use the same type, and don't mix old and new cells. When any of the cells go flat the others will soon follow, so replace all of them at once. If you use standard AA cells and buy in bulk they may be cheaper than any other solution.

• With somewhat more capable/modern/low-power op-amps, two nine volt batteries (otherwise the same) might work fine (+/- 9V, obviously.) With op-amps that can operate near the rails and circuits that don't draw large amounts of power, this is often sufficient, and compact.Please read the answer here WRT 358 and 741: electronics.stackexchange.com/questions/217834/… Commented May 8, 2016 at 2:53
• -1 for an uncritical recommendation to deliberately waste primary cells, especially to a newcomer. Commented May 9, 2016 at 7:09

For a stabilised output, you can buy IC7812(12V) and IC7912(for -12V). They require an input DC voltage which can be supplied from a battery(Li-on) or an adapter(mobile-charging adapter-little modification). You can easily rig up the circuit and have a proper stable regulated voltages for your opamp.

if you want only the 12v just get PC power supply old ones have +12v and -12v output