# LM741 op-amp, converting positive output to negative

I've got a few LM741 op-amps that I purchased by accident months ago, but now I'm in a situation where I believe they may be useful.

What I want to do is convert a positive voltage to the exact equal output, but as a negative.

So, if my input is +2.2v, I want the output to be -2.2v (actually the ranges are 0-0.237v). I have read quite a bit on how op-amps work, but a lot of the details go quite a bit above my head and quickly go beyond my understanding when I research what I'm trying to achieve.

It looks like I need to wire it as an "inverting amplifier" which I do understand how to do, but I don't know exactly what is required to ensure the output is exactly the same as the input, but reversed polarity.

My question is whether someone could possibly point me in the right direction as to how to achieve what I'm attempting to do (if possible with the chip specified).

• – Big6
Commented Aug 11, 2017 at 23:47
• To make this work you will need to provide both positive and negative supply rails. You might be able to get away with using one 9V battery to make the +9 rail and another 9V battery to make the -9V rail, but that's not guaranteed to work. LM741 wants more like +15V/-15V supply rails if I remember correctly. It definitely cannot drive an output voltage that is below its V- supply rail, so a negative supply voltage is required. See this canonical question about the limitations of the LM741: electronics.stackexchange.com/questions/304521/… Commented Aug 11, 2017 at 23:54
• Thanks to both of you thus far. I will follow up on the links. Commented Aug 11, 2017 at 23:57
• @MarkU I now see why the op-amps I have aren't ideal, thanks for the link. Requiring ~10v is kind of an issue, as I was hoping to run the rails at the same output at 3.3v (Raspberry Pi). I've learned quite a bit from this question both on the operation of the ICs and the limitations of specific chips. Commented Aug 12, 2017 at 0:47
• Pay attention to how much current you need the op amp tovvsource or sink Commented Aug 12, 2017 at 2:19