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I have ua741cn and connected it to 10V.

V_+ =10V

V_- =GND

Just to verify I have a valid chip I did a little test. I connected the non-inverting input to GND and the inverting to 10V I would expect the output be 0V but it was 2V. The opposite test did give me 10V at the output so the error is only in low output.

Is there any explanation and how to fix it? I tried to use different socket and chips but the same problem had occured

Thanks

DDonkey
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1 Answers1

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The 741 (a dinosaur that is well-past its sell-by date) cannot handle inputs close to either supply rail. If you want the input to reduce to 0 volts and get 0 volts on the output then you'll need a negative supply rail.

Reasons not to use a 741 op-amp tells you about this problem in the answer - see the main bullet point 2: Input voltage range is typically from -Vs + 2 volt to +Vs - 2 volt and main bullet point 7: Typical output voltage swing is -Vs + 1 volt to +Vs - 1 volt

Andy aka
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    Fully agree with Andy's answer, but I'd put it more drastically: Whoever forces you to use a µA741, kick them in the shins and run. Get a better Opamp. That thing should be dead since ca 1980. It still survives because there's people still copying electronic magazine articles from before that without understanding fully what they're doing. – Marcus Müller Sep 09 '20 at 17:41
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    I notice every time a "741" is brought up the poor poster gets jumped on for having the audacity to use such an antiquated device. But as is usually the case, the 741 is not the cause of the stated problem. Any standard opamp will have the same issue. Only a specialty "rail to rail" opamp will have outputs that go all the way to the rails. – td127 Sep 09 '20 at 18:14