operational amplifier shematic problem 741

[FvM]

Some manufacturers are specifying 5V minmal supply voltage for UA741, but without any guaranteed input or output voltage range. As said in post #1, single supply operation is intended however, and thus UA741 clearly isn't suited. Any OP with a common mode including the negative supply and suitable out voltage range will work, e.g. LM358 and LM324. At low output voltages, the amplifier can't sink current, this is a basic restriction of single supply operation.

P.S.:

the supply that i whould output is 80 mV

You previously told about 80 mV input rather than output voltage, buth both should work.

 

[yassin.kraouch]

:
buth both should work.

using LM358 will work or with the ua741 ?

 

[FvM]

As stated above

UA741 clearly isn't suited

 

[LvW]

He wants to amplify a DC signal, how is this going to work with an amplifier that has a unity gain?
Alex

Sorry, I didn't realize that he wants to amplify a dc signal.

 

[jjpl2001]

Dont loose your head trying to see what is wrong with the schematic!!!!, Go and change the m....king amplifier!! I did the same mistake until I changed to a Texas intruments amplifier TL071 TL081 or TL061 works fine, Im doing my thesis and at laboratory we made various tests with an oscope so what we found is that the 741 has a very bar response to frecuency, it reaches the saturation point very fast, Dosent have the same behavior beteewn one 741 and other (manufactury differences) and things like that, even an unity gain amplifier behaves bad!!! The same thing with LM324 and LMxxx. Best regards

 

[FvM]

TL071 TL081 or TL061 works fine

Although I agree to your general statement about the restrictions of LM358 and similar types, they'll serve there purpose for the present problem (single supply DC amplifier), but TL0xx would fail due to it's restricted common mode range.

 

[jjpl2001]

Although I agree to your general statement about the restrictions of LM358 and similar types, they'll serve there purpose for the present problem (single supply DC amplifier), but TL0xx would fail due to it's restricted common mode range.

yeap, its true, but I think that LM's have the same problem, BTW the TL0xx are good for the job that he wants here... Ive tested it

---------- Post added at 09:33 ---------- Previous post was at 09:30 ----------

Although I agree to your general statement about the restrictions of LM358 and similar types, they'll serve there purpose for the present problem (single supply DC amplifier), but TL0xx would fail due to it's restricted common mode range.

Restricted??????

https://winsunhk.en.alibaba.com/product/430130763-212088392/TL071_TL0

 

[FvM]

Restricted??????

A common mode starting 3 V above negative supply should be designated so. OP's enabled for single supply operation are expected to have the negative supply included in the common mode range. This feature is also required for the present problem. LM358 has it.

 

[jjpl2001]

A common mode starting 3 V above negative supply should be designated so. OP's enabled for single supply operation are expected to have the negative supply included in the common mode range. This feature is also required for the present problem. LM358 has it.

well, despite our common voltaje disscusion I can say that yesterday Ive tested the schematic that he displays here and it Doesn't worked with any of may (11) 741, And it works with the TL074. (I have 11 because I was thinking that the problem was a defective lm741)

Continuing our discussion what I've found that Texas Instruments Offers reliable datasheet measurements and real information (not only theoretical design data as LM's do) TI offers in their datasheets, information about capabilities, known configurations, known bugs!! and It seems that they know the problems of the common people that makes simple projects with the op-amps, so the offer too data about how their engeneers solved those problems, even more!!!, they offer statistical data about how much is the probability to buy a burned or a defective chip. So all that information about what a TL0xx cant do is more reliable than a theoretical LM datasheet (I say theroetical because Ive seen that 741 dosent do what they are supposed to do even with the configuration offered in their datasheets). So my invitation is to go ahead and do this schematic with bouth LMs an TL0xx and as me, watch the result in a oscilloscope.

Other thnig because that I say that LMs offers only theoretical data is because the 741Datasheet says that: "Input common-mode voltage range includes ground" exactly as the LM358 datasheet, and for me and after various laboratory tests is clear that 741 dosent have that common-mode range!

 

[FvM]

741Datasheet says that: "Input common-mode voltage range includes ground"

Please show the reference. I don't believe it.

 

[jjpl2001]

Sorry, my mistake!, it was the LM324 datasheet, I did have problems with that op-amp too so I included all those datasheets in the same folder. Not the same herratic problem as the 741 but my thesis circuit didnt worked with lm324 lm348 lm3900, I have a 324 working as a bandpass and anplifier and it works not just fine but it accplish the job