It is the same as U5A, as U5A, and U5B are the two channels of TL082 opamp

What I mean is, this is a simulator. We don't know all the rules or what happens in a simulator.
Either connect pins 4 and 8 as with U5A or use another device such as U7.

 

Do it like this:

 

hi MMM<
Created a TL082 model.
Add the 10K's to the inputs to 0V
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You power supply for the opamp is +3V and -3V. The inputs to the opamp need to be in the common voltage
range which for +3 and -3 power is +3+.1 and -3+2 or +3.1 and -1 volt.

You are still looking at the datasheet for a New TL082H but he is using an older TL082.
Maybe simulator programs also do not know about the New H version.

 

hi,
This result, below -2.1v is using an older TL082 model.
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Could you try changing the supply voltage to ±5 and see what you get?

 

Changing the supply voltage for a simulation won't make any difference because the simulation uses a model with "typical" specs.
The datasheets show circuits using a minimum supply of +5V/-5V.
When you build the circuit then some TL082 devices with minimum spec's and supplies that are only +3V/-3V Will Not Work.

I design circuits observing minimum and maximum specs so that ALL circuits work properly, not just circuits with devices that have "typical" specs, then I do not need to sell the ICs or circuits that don't work on ebay.

Of course the simulation works fine when using ADTL082 opamps having "typical" specs. Some of the ADTL082 opamps also will not work with a +3/-3V supply if the opamps have minimum spec. They will work the same as Texas Instruments designed them, barely working when the supply is +4V/-4V. The datasheets show circuits using a minimum supply of +5V/-5V.

 

Do it like this:

First, I have reversed U6A to obtain a positive value.
Second, the output is still wrong, it should be 4.2V instead of 3.48V (>17% error)

 

hi MMM,
I don't have a TL082, used a typical low power rail OPA,
The typical 3 OPA/INA circuit works as expected.
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View attachment 282381

I will not be able to get the MCP6001 chip, so I cannot use it.

 

Hi MMM.
You don't have to use, a MCP6001, just buy an up-to-date genuine TL084.
Look at Post #25

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The TL08x is 45 years old and can use a supply that is +5V/-5V.
A new TL08xH is 7 years old and can use a supply that is +4.5V/-4.5V.
Some of them have inputs that Do Not work if their voltage is less than 4V above the negative supply.

 

hi agu,
Checkout this PDF.
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I changed the TL082 Op-Amps to TL072 Op-Amps, got the same output voltage. I think there is an issue regarding the circuit not the Op-Amp used.

 

Yes, the new TL08xH is much better than the old one. It will work fine with a +3V/-3V supply.
Today Digikey and Mouser have some TL081H in stock but no TL082H nor any TL084H. Surface-mount only.

 

I changed the TL082 Op-Amps to TL072 Op-Amps, got the same output voltage. I think there is an issue regarding the circuit not the Op-Amp used.

hi MMM,
Do you have a photo of the project you could post.
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The output of U4A is saturated as high as it can go (+3.58VDC) because its inputs were wrongly swapped.
You had the inputs correct a while ago. Here is a circuit from the AD620 instrumentation amplifier datasheet:

 

hi MMM,
Do you have a photo of the project you could post.
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All what I need to do is constructing an instrumentation amplifier that could amplify low level signals such as 1mV, 2mV, ... You can forget about the 100mV, and 200 mV I used before. I started by amplifying the 100 mV as it is closer to 5V than the 1mV, so I assumed it was much easier. So, I need to amplify these low level signals with gain 2000, also I started with gain 21 because it is easier to amplify the signal 21 times than amplifying it 2000 times.

 

Yes, the new TL08xH is much better than the old one. It will work fine with a +3V/-3V supply.
Today Digikey and Mouser have some TL081H in stock but no TL082H nor any TL084H. Surface-mount only.

I reversed the polarity again, but the problem is the negative output.

 

Yes, the new TL08xH is much better than the old one. It will work fine with a +3V/-3V supply.
Today Digikey and Mouser have some TL081H in stock but no TL082H nor any TL084H. Surface-mount only.

I really need to use modern chips, but these modern chips are not available in our local stores. Thus, I have to use old ones.

 

hi MMM.
What other types of OPA's do they have in stock?
We may be able to suggest an alternative type.
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