Your Op-amp needs this power supply circuit

Hei there, welcome to another tutorial from Aaenics. Today we want to learn something special when it comes to working with Operational amplifiers. Its more like a skill which will help you in your endeavor in electronics and circuit design in general. If you don’t know what an Op-amp is yet, thats very bad, do well to check out my previous article, Introduction to Operational amplifiers, which will get you more comfortable with this present tutorial. Else, lets do this thing!

Most Circuits Need a dual power supply!!!

In my early days of building circuits i realized some circuits need more than just +Vcc(positive voltage source)and Gnd(ground or 0 volts). A clear example is the LM358 op-amp and most other op-amps and ICs you will find yourself using in time. Some circuits actually require -Vcc(negative voltage source) too. There are some table top power supplies you can get for a few cedis that can give you +Vcc, -Vcc, ground and perhaps other voltage levels but the circuit we are going to build today will get you +vcc, -vcc and ground for powering your op-amp and the other circuits that may require it. Its called a Passive Dual DC Power Supply. Its passive because we are not going to need any active element in our circuit to get us what we want.

How to build a passive dual DC power supply.

This is a schematic diagram of what is to be built.

This is also a virtual breadboard view of the circuit.

  • DC 9v supply
  • Jumper wires
  • Two capacitors of the same value, I used 220uf for this tutorial.
  • Two resistors of the same value, I used 220ohms for this tutorial
  • Bread board
  • Get your breadboard in place
  • Connect your battery to the power rails of the breadboad.

  • By means of two jumper wires, get both rails of the breadboard powered with your 9v supply.

  • Get two resistors of the same value to build a simple voltage divider network  between vcc and gnd.

  • Now since both resistors are of the same value, the midpoint will be 0.5Vcc that’s half the supply voltage.
  • From the picture above, the yellow jumper wire is the mid point of the voltage divider where the 0.5vcc will be established and that’s where will be the new ground(gnd) for the circuit. If you use a 9v battery you will have approximately 4.5v across both resistor. I say approximately 4.5v because you may sea a slight shift because of tolerance.
  • Your dual power source is almost ready. The middle of your voltage divider where the two resistors meet is your new ground(gnd or reference point). The two other extremes which were previously vcc and gnd are now your +vcc and -vcc respectively. You can verify this by using a multimeter to read the dc voltages at the extremes, using the midpoint as your gnd.
  • The last step to complete your circuit is to fix two capacitors of the same value across both resistors. The work of these capacitors is to stabilize the new voltage levels when you connect your external loads to it.

Alright then, congratulatons if you have this done. You now know how to build a dual power supply, out of a single dc battery. You will be needing this circuit’s idea to power most of your future projects.

Where can I buy electronics in Ghana?

Check out the Aaenics store for a wide catalogue of both local and international Electronics and Robotics kits and components. Order for anything and get it delivered as soon as possible every where in Ghana.

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