741 Op-amp Not Working…

I'm building as small project in which i need some DC gain...So i decided to use the UA741CP op-amp in my circut when i designed the circut on simulators it worked perfectly i use a non-inverting ampifier with 1 v dc input and a gain of 11...So the output voltage must be in the range of 11 volts but when i put it in real life it gives me 0.69 volts i re-connected it a million times with the same result...Please help i don't know what to do.

Your power supply might be the issue. What are your ground and v+ levels for the opamp? Are your input and output signals in the operating area for the 741 (it can't operate with inputs or outputs close to the rails).

Well,I'v used 15 volt power supply (as mentioned in the datasheet) to bais the op-amp,and i'v checked the datasheet for the limitations and i don't think it is near the rails anyways

Have you tried different 741 parts? Your opamp might be dead, 0.69v out is a common failure mode, one diode drop above ground...

I would try building a buffer (without the feedback resistors) and see if you get a reasonable output (output voltage should be the same as input). Next I would use two 10k resistors and see if you get a reasonable output for that.

Please clarify the power supply issue, do you mean you have used plus and minus 15 volt rails?,
cheers,
Richard

When i put a 2 10k resistors the output is the same is about 0.7...i think its a diode drop as you said,So what can i do about it...??

Thanks a lot for trying to answer my question

First, take a look at Richard's question. Are you using a single 15V supply? Most 741 opamps require at least +/- 10V to operate which is 20V between V+ and V-. if you only have 15V you might be operating the chip outside its specification range. The TI 741s require +/- 10V, other manufacturers parts might have different requirements.

Otherwise, try removing the two resistors and making the circuit as simple as possible. Look at the buffer schematic here: http://www.eecs.tufts.edu/~dsculley/tutorial/opamps/opamps5.html

Next, make double-sure you know how the pins are numbered, when starting out I recommend people draw the chip with pin numbers and the draw the circuit they plan to assembly around the chip. This significantly reduces the error rate.

After assembling the buffer circuit, use a multimeter and check the potential (voltage) of every pin against ground, write these all down on your drawing made above.

If everything looks right, but the circuit still doesn't work, get another (hopefully known good) 741 chip and try that. Check the temperature of the chip while operating, it should be room temperature.

If it still doesn't work, post a list of the pin numbers and their associated voltages from above and we might be able to help.

You might also take a look at the signals on each pin with an oscilloscope if you have access to one. The should all be flat DC levels, if you see anything else then you have a hint as to what the problem is (power supply with ripple or just AC voltage on output, 1V source is not DC,etc etc).

Good luck.

Thanks Again for responding and I'm sorry for taking so long to respond but I'm having a hard time Dealing with the "600 Seconds" limit for commenting.

I've done the drawing you asked me and it made the connecting so easy but the result is the same.

I put a 32 voltage supply to bais the chip as you said it is better to be more than 20 volts.and when checking every pin against ground i was surprised to find that the pin 5 (offset null) have a -11.25 volts against ground and i should be zero...i cant find explanation for this so far.

And about the ripple unfortunately i don't have any access to an oscilloscope but i do think that their is a ripple as the multimeter is not stable while the input voltages are stable on the same multimeter.

Thanks again for giving me some of your precious time.

As Dean said, post your drawing, include on it all of the wiring/component information, and all voltages on the pins of the 741.
The voltage on the offset pins should be close to the voltage on pin 4 of the 741, this may be inferred from looking at the schematic of the 741.
If you can, also post a photo of the complete set up, with as much detail as possible,
cheers,
Richard

Well,I have a little update to say...
I was using the supply all wrong that i didn't use a +/- bais volts so when i did that the chip worked.I can't say i worked well because the gain should be 11 and i'm getting about 3.4 i'v tried to change the resistors but nothing is happening i'v changed the chip hoping that it will work .

Here is the design That somehow worked but i'm not sure.

In that design I'v used a second Chip as a buffer as to create a virtual ground so i can get + and - 15 volts supply.

Thanks for your time Richard.

With a circuit like you are using, you have to be careful that the supply is really floating, that is, it's likely to be a battery. Some power supplies derived from the mains will have one side grounded.
Without knowing precisely what you are using, it's hard to know what to suggest, hence my request for a photo of your setup.
With respect to the output voltage you are getting, have you measured the input voltage as well, to verify it is what you think it is?
Download this book from TI, and have a good read of appendix A, a good section about single supply op amps.
http://123.physics.ucdavis.edu/week_1_files/opamps.pdf
It may help you decide how to go about a single supply design.
Cheers,
Richard

The input bais voltage is what i needed as it is -15 and 15 relative to ground of course if that is what you meant...
and i'm new with the usage of ICs so please give me simple instructions...
Thanks again

Good, you have apparently sorted out issues around the power supply.
Do you have a DVM. If so, make all the measurements that we have asked for, put them on a drawing, and post it. The voltages are best measured with respect to the "ground"
If we had known what you had done with the power supplies early on, it would have avoided many of the problems that you have been trying to deal with. We are floundering around in the dark as much as you are for lack of information.
Your diagram I take it is from a simulator, you have to be wary of simulators, you have to understand what the model of the op amp is like, basic ones will not simulate an op amp correctly, they won't take into account how close the inputs and outputs of the op amp can swing to the positive and negative voltage rails, for example, and may not care what the power supply rail voltages are as well.
Before using a simulator, you must have a basic understanding of how an Op Amp works, and some of the typical parameters you have to deal with in designing with them.
The book that I suggested from Texas Instruments is a good intro to Op Amps (free PDF download), there are plenty of others, try and get hold of a copy of "The Art of Electronics" by Horowitz and Hill, for example,
cheers,
Richard

I think you are right about the simulation point.And i'v downloaded the book you gave me and read it also I'v done what it ordered me to do but so far no result.
About the lack of information maybe you are right again but I'm trying avoid that as possible.
So this is the diagram of the voltages around the Chip.Hoping you can help me with it.

OK, the power supplies look alright.
An Op amp with negative feedback drives the output in such a way that it makes the two input voltages the same. If you have 1V on pin 3, then the output should drive the resistor network so that there is 1V on pin 2. This assumes that the inputs and output stay in a linear region.
Why isn't it working. There could be a few reasons for that, the 741 is oscillating (generally hard to get them to oscillate, capacitor on the output would do it). This is hard to see without a scope.
Severe ripple on the power supply (where are you getting your supply from), again a scope is useful.
Have you put decoupling capacitors on the power supply pins.
Damaged 741.
Please could you send a photo of your set up, power supply details, what is your 1V source, how have you assembled it, on perf board, etc,
cheers,
Richard

Well Richard I'm so thankful for you for your help and this is so nice of you to spend your time on helping me...I'm really really so thankful for you.

The problem of the scope is huge to me and i'm trying to find a solution for it but every solution need money and Money is a bigger problem.

About the supply i'm constructing a power supply with a variable regulator LM317 to produce about 32 volts regulated.The schematic is attached.

The signal i am amplifying is from an arduino chip from the PWM pins ( pin 5 for analog) where i have exactly 1.00 volts.

on the bread board the blue and white jumpers are the signal from arduino
And the green and white wires are from the supply

I think you are being bitten by several things here.

1. You need capacitors on the output of the LM317. A 10uF in parallel with a .1uF would be ideal.
2. You need bypass caps around the 741, a 0.1uF cap as close to the actual pins as possible is ideal
3. The output of an arduino when using analogWrite is not actually an analog signal, it is a PWM signal which means it toggles between 0V and (typically) 5V rapidly with the average voltage equal to the value specified in analogWrite. You need an RC filter on the output to smooth this square wave into a more DC-like signal.
4. It is very difficult to tell using a voltmeter if your DC signal has an AC component riding on it (like the PWM signal).

You can build a really cheap oscilloscope suitable for this task and a few other audio frequency projects (not a real replacement for an oscilloscope) using an arduino for cheap: https://www.element14.com/community/community...le-diy-oscilloscope-with-arduino-uno-and-mega

There are several other articles around including many that do not require an LCD shield. Note that any of the examples that use analogRead and Serial.write in the main loop without storing the values in an array should be ignored (too slow). You need to acquire using analogRead into an array and then dump the array at the end of the sampling interval. It will be very limited in speed, accuracy and noise but it will let you see slow signals between 0 and 5V.

OK, so at last we are getting some useful information. I was making too many assumptions on what you were doing.
Dean's suggestions should be followed.
Additionally, to check that the 741 has the correct DC gain, remove the present driving source, and apply a DC voltage to the op amp input. Best way to do that is with a voltage divider (say two series resistors of between 1K and 10K) across a 1.5V alkaline cell. Apply the voltage from across one of the resistors between your ground and pin 3 of the op amp. Measure the voltage between pin 3 and ground(should be arond 0.7-0.8 Volts for a new battery), and at the output, the output voltage should be 11 times the voltage on pin 3 (the voltage on pin 2 should be the same as on pin 3)
What is the 741 going to drive, it can't supply much current, and the circuit for driving the pseudo ground has current limitations as well.
If your DMM has an AC range, it may have a response from below 50Hz to perhaps 5kHz, or more on a quality meter. That may be enough to see if you have AC voltages on your power supply and signals. Note that it is only an indication, you won't get useful readings at low voltages or where the frequency is well above the frequency range of the meter.
Cheers,
Richard

Well,Richard i have some amazing news...The op-amp just worked perfectly.
I'v followed Dean's advice to see the signals on the Oscilloscope and what i saw was a big surprise...The op-amp is amplifing the signal quite well but due to the arduino's PWM pins the output was oscillating so my voltmeter wasn't detecting the full signal just the DC part of it.and this means that my circut is good and the arduino is the devil here.

I just want to thank you a lot for your time you and Dean.And I'm full of hope that i would be able to pay this back one day...