For sometime I have wanted to get to the bottom of this. Thanks for posting, it has provided some answers. On 2 Dec 2017 21:58, "RussellMc" wrote: > I'd call it a draw OR a lack of clear definitions. > > *IF* you deem single supply to mean "Input signals can be ground referenc= ed > with more or less correct operation" then the LM741 fails with a 2 or 3 = V > out of range area wrt ground with a 30V single supply > > If you deem single supply to mean "supply is 0V and +xxV and **signal** > ground is somewhere between these" then an LM741 can operate "single > supply" subject to common mode restrictions. > > Ref: Revised TI datasheet October 2015 > https://media.digikey.com/pdf/Data%20Sheets/Texas% > 20Instruments%20PDFs/LM741_Series_Rev_July_2016.pdf > > The data sheet mentions "common mode range" 7 times BUT only defines it f= or > a 30V (or +/- 15v) supply. > At 30V between + and - rails Vcm is +/- 13V typical and +/- 12v min. > ie for design +/- 12v should be used - ie Vin cannot be taken with 3V of > either rail (or withn 2V typical). > The datasheet does not make it clear if this value alters with resucing > supply anmd, if so, whether it gets better or worse. . > In the absence of clarification Occam says to use the values iven - but > Murphy laughs. > > That means that on a 6V total supply Vin allowable range is 0V and even a= t > 2v dead band the allowable Vin is 2.5V +/- 0/5V with a 5V supply. > > That the person using 5V supply "had trouble" is unsurprising. If they ha= d > made it work it would have been remarkable. > > Even "single supply" opamps that claim rail to rail operation often mean > "almost rail to rail" - especially on outputs. > Genuine RR in and out amps use internal power converters to produce > internal rails outside the supply rails. > > > Russell > > > > > > On 3 December 2017 at 01:17, James Burkart > wrote: > > > As I was re reading this email I noticed that he made some edits since = he > > first posted, specifically the last thing he mentions about it working. > > After going back I saw that he added an edit to one of his posts. > > > > Him: The operating conditions for all tabular data and for every graph > > stipulates split supply operation. > > > > You won't find a any reference to single supply operation on any spec > sheet > > for the 741 from any manufacturer. EDIT: I checked the most recent > (2015) > > TI specification and it says "The LM741 can operate with a single or du= al > > power supply voltage." All tabular data and graphs still stipulate > split > > supply operation and the common mode range still doesn't include ground > > when a single supply is employed. > > > > A single supply op amp is specifically designed to have a common-mode > range > > which extends all the way to the ground. Its output stage is usually > > designed to swing close to ground. The 741 does not incorporate either > of > > these design attributes. > > > > > > On Dec 2, 2017 4:53 AM, "James Burkart" > wrote: > > > > > Over on reddit (r/AskElectronics) a guy was having troubles getting a > > > circuit to work. His problem was that he was using an LM741 with a > single > > > 5V supply and expecting it to operate near the rails. Everyone was > > helpful > > > and explains the 741's limitations and suggested another opamp. But I > > took > > > issue with what another redditer said, that the LM741 was not designe= d > > for > > > single supply operation. The following was the discussion that > followed. > > Am > > > I just completely wrong? > > > > > > > > > > > > Me: I wouldn't say that it's "not designed" for single supply > operation. > > > Just gotta know that it's not a rail to rail opamp and so in single > > supply > > > operation it's output can never reach 0V, which happens to be it's > > negative > > > rail potential. > > > > > > Him: It's actually not designed for operation from a single power > supply. > > > Not my opinion it's straight from the Fairchild specification sheet= .. > > In > > > fact it kinda, sorta, operates with a single power supply but will no= t > > > perform as specified. > > > > > > Me: Where in the Fairchild spec sheet does it say that? > > > > > > Him: The operating conditions for all tabular data and for every grap= h > > > stipulates split supply operation. > > > > > > You won't find a any reference to single supply operation on any spec > > > sheet for the 741 from any manufacturer. > > > > > > A single supply op amp is specifically designed to have a common-mode > > > range which extends all the way to the ground. Its output stage is > > usually > > > designed to swing close to ground. The 741 does not incorporate eith= er > > of > > > these design attributes. > > > > > > Me: There is no ground pin on the 741 so the amp isn't even aware of > > where > > > ground is. Single supply or split supply, the thing works exactly how > > it's > > > supposed to. Obviously one needs to design the circuit to operate > within > > > the capabilities of the components used, so if the designer needs the > > amp's > > > output to swing negative then he's obviously going to use a split > supply. > > > But if he doesn't need the output of the amp to drop below 2V, or his > > > circuit requirements allows him to float his ground, then unless > another > > > part of the circuit requires a split supply, there is no need to use = a > > > split supply, and the 741 will work exactly to spec, assuming all els= e > in > > > the circuit design is correct. > > > > > > Him: If it's operating on a single power supply the negative pin is > > > connected to ground. Common mode operation does not include ground s= o > it > > > will not meet specification. That said if you can keep the input > within > > > the restricted common mode range, about 2V above ground, it will work= .. > > > > > > > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .