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Saturday, 2 June 2012

Op-amp +/- Power From Single Supply Fragment Stripboard Veroboard



a simple little circuit that will help anyone really new to electronics. you'll see a lot of circuits that have ICs that require a split power source IE +5 volts and -5 volts, there are quite a few ways of achieving this, ranging from the full on voltage regulator method (so you have a LM317 and a LM337 with a center tap transformer) to charge pumps or you can use a voltage divider or in the case I have laid out, a voltage divider with a unity gain buffer to give you a virtual ground. basically the circuit splits the input voltage in 2 and makes a center reference point between the 2 voltages - that's the really stupid way of explaining it anyway.

for the sake of better performance (especially for you audioweirdos) I have included capacitors on the input however usually I wouldn't bother including them because I put filter caps on the main power supply but I put them on the layout for the sake of completeness.

it maybe worth noting that if you saw my headphone amplifier circuit earlier on, I used a different type of voltage divider, quite similar to this without the op-amp buffer but instead of giving me dual voltage supply, that one gives me a Vref of half the Vin.

anyway here is the circuit


14 comments:

  1. I saw your circuit and I am trying to get a dual polarity power supply from a single 5V dc supply. But what your circuit really does is to split the voltage rather than give the positive and negative polarity so that I can feed dual polarity voltage on to the op-amp. What can be the solution for that? Please help.

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    1. well if you put 5 volts into this you would have +2.5v and -2.5v referenced from the virtual GND
      this is a very common way of powering dual polarity circuits - in fact it is probably the most common way.

      I suggest you breadboard this circuit if you don't believe me.

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  2. Actually I already tried it on breadboard. I wanted to use it to give dual power to an op-amp LM392. However, I am not sure how to give it through this circuit because when i measured +vout and GND from multimeter it gave +2.5 V and similarly when i measure -vout and gnd it also gave +2.5 V.

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    Replies
    1. you've done something wrong - try looking at the polarity of the capacitors for example. double check

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    2. switch the positive and negative, the ground should be at the virtual ground and the "positive" should be at the negative output

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    3. honestly dude, I've used this circuit hundreds if not thousands of times - if it's not working how I have described then the problem is at your end. it is all labelled how it should be.

      here is a picture of it http://4.bp.blogspot.com/-iyTMhUkew4I/UYRUGo5wh2I/AAAAAAAAAkI/UXL1vOieb5M/s1600/P5044875.jpg

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  3. Great lttile circuit, works a treat ... thanks :)

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    Replies
    1. cheers dude. I'm not exactly sure how the dude above is having difficulty with it (or was having difficulty)

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  4. Hello, I would like to ask you very kindly why when I'm connecting the corresponding resistors to obtain a suitable gain for the op-amp, so the bipolar source is not anymore symmetric. In my case is giving more negative voltage than positive. Could you give me some advice please? . I'm trying to make ac active low pass filter and I don't know what I'm doing wrong.
    Thank you in advance for your help my friend.
    Best regards
    Steve

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  5. it depends how much it is out by. but the usual reason is because the resistors aren't exactly matched.
    essentially this is a voltage divider so if the resistors are exactly 100k you will get an evenly divided voltage however if one resistor is out by even a little bit it can make a big difference. so measure the 2 resistors before you put them in the circuit.
    they don't have to be exactly 100k but they have to be exactly the same as each other

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  6. Hey,

    Thanks for sharing this neat circuit. Can you tell me how many amps can it handle? I am planning on using it to power 6x TL072 op-amps.

    Alex

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    1. I'm not sure - you'd have to try it out. personally I would use 3 TL074s or even the TLC074s and dispense with the dual supply altogether (FYI there is a TLC072 also)

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    2. I can't really change the op-amps right now, as I already made the PCB's for my project, everything is soldered together, and remaking everything would take me just to much time. I measured the current consumption, and the results I got was 20mA per rail, so that means 40mA per total, I guess, that's a little to much for a circuit like that? What do you think?

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  7. Would this work for +/-12? Looking for something to power a Eurorack circuit...

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