# How to get the 741 op amp to work as a linear amplifier?

I'm trying to run the 741 as a non inverting voltage amplifier.

I did the circuit in proteus simulation and it works well to get 2x the input signal.

For example, if input voltage is 1V, then I get 2V on output pin.

So for this implementation, I the same circuit on the breadboard:

But on the breadboard, I connected the exact circuit but it doesn't work as expected!!

This is my video on YouTube explaining the problem:

ua741cn non inverting amplifier problem

============================================================================== I have another question:

Can I use 12V source and split that by two 10k resistors and supply +6V and -6V to the op amp like this circuit:

• A good first step would be not using a 741. – Hearth Mar 30 at 19:46
• Look at the 741 datasheet for minimum supply voltages. The 741 is a > 40 year old design and considered a poor choice these days. It works on the simulator because the simulation is faulty. – Transistor Mar 30 at 19:47
• wrt your 2nd added question, yes you can try that, it won't hurt anything, and you will learn things. – Spehro Pefhany Mar 30 at 20:58
• @SpehroPefhany Thanks, that's good to know that my way of putting another question isn't completely wrong. – R1S8K Mar 31 at 2:11
• @Transistor You're right, I should try to add another -5V voltage. – R1S8K Mar 31 at 2:13

5V is not enough for the LM741 to work properly. It needs a minimum of +/-5V

Also the input common mode range does not include the negative rail, so the inputs are not going to be functional.

The output can typically swing okay to +2 with a light load (though 667 ohms is not a very light load if the voltages get higher), so at least that part is okay (at room temperature).

You could plop down a different op-amp and it would work more-or-less as you intended, but this way you are learning something. Many very useful modern op-amps have limited input common mode range, and you should always pay attention to datasheet power supply limits (and output swing and loading guarantees).

Give it +/-5V supplies and it should work properly, but it would be better to increase the feedback resistors to somewhere in the 10K range.

To stay within datasheet guaranteed numbers, as a pro would normally seek to do, increase the supply to +/-10V and make sure the load resistance is at least 2K (including the loading of the feedback network). That should guarantee a +/-5V output range over the full temperature range of the chip.

• I updated the post with another question. – R1S8K Mar 30 at 20:53
• So, can I put a single 12V supply and split that with two resistors to get +ve and -ve voltage supplies? – R1S8K Mar 31 at 2:15

Your schematic says you are operating the 741 on 5V. That won't work.

The datasheet for the 741 says that your inputs must stay a couple of volts away from the voltage rails.

Valid input range is therefore between 2 and 3 volts when operating on 5V.

The datasheet also says the output can't get get any closer than 2V to the voltage rails. So expected output range when operating on 5V is between 2 and 3 volts.

Your simulator seems to treat the 741 as an ideal opamp, rather than respecting the limitations of the real 741.

You have run head first into the difference between theory and reality. The 741 is a very good example for this kind of thing. It is rather less than ideal. Good for learning how to deal with non-ideal things, not so good for real circuits.

• I updated the post with another question. – R1S8K Mar 30 at 20:53
• I added a -ve voltage, but I didn't get any amplification to a sine wave signal??! – R1S8K Apr 5 at 13:59