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.

No problem, as long as you supply it with the minimum voltage required, ±5V, and don't expect an output outside of ±2V.

 

I guess the correct schematic is inverting so you simply reverse the inputs to get a positive output.

 

Why don't you read the datasheet of the AD623 that answers all your questions?

 

Why don't you read the datasheet of the AD623 that answers all your questions?

Of course I should do this, but as a beginner it would be extremely difficult for me to understand everything in it. Also, I don't know if I am going to use this chip or not, so it would take too long time to read the datasheet of each Op-Amp to make a decision. Anyway, thanks for your comment

 

An AD623A is fairly expensive. Maybe you are a low income student?

 

I simulated the circuit on CircuitMaker 2000 using TL082 as per post #21.
With two 5V supplies and 100mV input, the output is -2.1V.
With two 3V supplies and 100mV input, the output is -1.459V.
With two 3V supplies and 70mV input, the output is -1.402V.
With two 3V supplies and 50mV input, the output is -1.050V.

Here are DC operating values with 10mV differential input.

 

An AD623A is fairly expensive. Maybe you are a low income student?

Yes, it is fairly expensive and I am a low income student, but I will be able to get one AD623 chip. If this will work fine for my purpose.

 

I simulated the circuit on CircuitMaker 2000 using TL082 as per post #21.
With two 5V supplies and 100mV input, the output is -2.1V.
With two 3V supplies and 100mV input, the output is -1.459V.
With two 3V supplies and 70mV input, the output is -1.402V.
With two 3V supplies and 50mV input, the output is -1.050V.

Here are DC operating values with 10mV differential input.
View attachment 282492

Many thanks for your contribution. This circuit is similar to the ones in the previous posts, and I could finally get those outputs. What I need is: amplify the low level signals such as 0.1 mV, 0.2 mV, ....., 2.5 mV such that the 2.5 mV be 5V, and the 0.00 mV become 0.00 V. So, I need to amplify with gain 2000. If you do this with TL082, you will not get what you need. So, I am searching for an alternative. The best one I have found is the AD623AN, so I am asking if it is suitable or not (practically not for simulation purposes), and I am wondering whether the circuit I have shown in post #45 is correct and feasible or I will encounter so many problems when implementing it.

 

Of course I should do this, but as a beginner it would be extremely difficult for me to understand everything in it. Also, I don't know if I am going to use this chip or not, so it would take too long time to read the datasheet of each Op-Amp to make a decision. Anyway, thanks for your comment

You don't have to understand everything in it, but you will never understand anything that's in it unless you start trying to. Furthermore, don't you think it's a bit unreasonable to expect everyone else to do it for you just because you don't feel it's worth your time to even try?

 

Many thanks for your contribution. This circuit is similar to the ones in the previous posts, and I could finally get those outputs. What I need is: amplify the low level signals such as 0.1 mV, 0.2 mV, ....., 2.5 mV such that the 2.5 mV be 5V, and the 0.00 mV become 0.00 V. So, I need to amplify with gain 2000. If you do this with TL082, you will not get what you need. So, I am searching for an alternative. The best one I have found is the AD623AN, so I am asking if it is suitable or not (practically not for simulation purposes), and I am wondering whether the circuit I have shown in post #45 is correct and feasible or I will encounter so many problems when implementing it.

What does the data sheet say?

https://www.analog.com/media/en/technical-documentation/data-sheets/ad623.pdf

Just look at the features listed on the first page and it will answer your question.



One thing I haven't seen is what kind of signal you are trying to amplify. More specifically, what is the bandwidth of that signal?

 

You don't have to understand everything in it, but you will never understand anything that's in it unless you start trying to. Furthermore, don't you think it's a bit unreasonable to expect everyone else to do it for you just because you don't feel it's worth your time to even try?

I have mentioned above "I should do this". Thus, I understand how worthy it is to read the datasheet, this is always recommended. Also, I do not expect anyone to do it for me, I just need some help, If you go to the beginning, you will find that there was a circuit that I designed and I want to know what was wrong with it. That means I have already tried before asking, and I am still trying. Anyway, your comment is appreciated

 

What does the data sheet say?

https://www.analog.com/media/en/technical-documentation/data-sheets/ad623.pdf

Just look at the features listed on the first page and it will answer your question.

View attachment 282505

One thing I haven't seen is what kind of signal you are trying to amplify. More specifically, what is the bandwidth of that signal?

As shown in the image, I will not be able to amplify with gain 2000 because the gain ranges from 1 to 1000. However, the simulation shows that gain 2000 is feasible, that is why I am asking about the hardware implementation of that circuit as you have more experience in this matter. I really do not know what the bandwidth of that signal because I am using DC in the whole project.
Thanks for your comment

 

As shown in the image, I will not be able to amplify with gain 2000 because the gain ranges from 1 to 1000. However, the simulation shows that gain 2000 is feasible, that is why I am asking about the hardware implementation of that circuit as you have more experience in this matter. I really do not know what the bandwidth of that signal because I am using DC in the whole project.
Thanks for your comment

So the input signal that you are amplifying never changes? That's the only way it can be DC.

What is it that you are measuring? What is "that signal"? If you describe what it is you are trying to measure, we might be able to help you get a feel for what kind of bandwidth you need.

If you try to get a gain of 2000 with that part, you are operating it outside its specified performance envelope and there is NO guarantee that it will work at all. Worse, the first one you use might work fine, but when you build another system or replace the part in the original one for whatever reason, it may not work.

One option is to use a multistage amplifier. With two stages you would only need a gain of 45 in each stage. Or you could get most of the gain from the first stage, say 200, and then only need a gain of 10 in the second stage. The smaller the gain per stage, the higher the bandwidth -- which brings us back to needing to know something about the bandwidth of the signal you are trying to work with.

 

So the input signal that you are amplifying never changes? That's the only way it can be DC.

What is it that you are measuring? What is "that signal"? If you describe what it is you are trying to measure, we might be able to help you get a feel for what kind of bandwidth you need.

If you try to get a gain of 2000 with that part, you are operating it outside its specified performance envelope and there is NO guarantee that it will work at all. Worse, the first one you use might work fine, but when you build another system or replace the part in the original one for whatever reason, it may not work.

One option is to use a multistage amplifier. With two stages you would only need a gain of 45 in each stage. Or you could get most of the gain from the first stage, say 200, and then only need a gain of 10 in the second stage. The smaller the gain per stage, the higher the bandwidth -- which brings us back to needing to know something about the bandwidth of the signal you are trying to work with.

Ok, I am working on a weight sensor, this sensor only gives a DC (using oscilloscope to view the signal, it was very close to a DC as long as the input is the same, when a change occurs in the input, the DC level will change but it is still DC). I just want to mention that there is no AC source, capacitors, or inductors, Thus, I think it is totally DC.
Again, many thanks for your contribution, this opens a new door for me to look for other ways

 

hi MMM,
Do you have a datasheet for the weight sensor or a link.?
E

 

hi MMM,
Do you have a datasheet for the weight sensor or a link.?
E

The maximum output was 5.5 mV at max load, and 5V input source

 

hi MMM.
A photo does not help.
We need the specification.
E

 

hi MMM.
A photo does not help.
We need the specification.
E

https://www.amazon.com/Uxcell-a1407...670492562&sprefix=load+cell+1k,aps,201&sr=8-4


The specs are written in the description of the product. I could not find its datasheet because I don't know the model of that weight sensor

 

hi MMM,
I have one of those, the elements are 1K each, use 5Vdc and it outputs 1mV/Volt.
So full scale 1kG gives 5mV.
They work well with the HX711 load cell amplifier and data output.

What are you driving with the INA amplifier output voltage.?
E

 

hi MMM,
Please try this battery connection with your circuit +4.5 and -1.5V
Using your TL082 OPA's
V3 is a test 5mVolt voltage for the output of the load cell at 1kG load

Let us know what you see
E
R9,10,11,12 are the resistive elements of your load cell bridge