TL031 Differential input Voltage Curves

[albert22]

Hi,
I dont understand the VO vs VDI curves (figures 19 and 20) shown in the TL03x Datasheet.
https://www.ti.com/lit/ds/symlink/tl031.pdf
From fig. 20:
How can the the output voltage could be 0.5v when the differential input voltage is 10v?
Also it is shown that the output voltage is higher when RL is smaller. How can this be?
As far as I know an op amp saturates with just mVs of VDI.
Please explain.
Thanks and Regards

 

[godfreyl]

Please explain.

Hi Albert

Your reasoning is correct, the graphs are labelled wrong in the datasheet.

Horizontal axis should be output(in Volts)
Vertical axis should be differential input voltage (probably in mV)

Unfortunately, people make mistakes so sometimes wrong information is printed in datasheets and books. When I see something suspicious in a datasheet, I try to find a couple of other datasheets for the same part number and compare them. That can help to clear up the confusion. Other times (like in this case) it's obvious the datasheet is wrong.

Regards - Godfrey

 

[Analog Ground]

Figure 19 for 5V supplies is also incorrect. IMHO, this is a bad error for a data sheet which has been around for over a decade. In their defense, I think this is not a very common graph for an op amp. The main thing it shows is the output swing is greater to the positive supply than the negative direction for larger loads. This type of info is usually given with a different graph which does not include large signal gain characteristics.

 

[godfreyl]

Figure 19 for 5V supplies is also incorrect.

Yes. Sorry, I should have been clearer - my comments apply to fig 19 and fig 20.

 

[albert22]

Thank you guys. I could not believe that TI made such a mistake (really two). I checked several op amps from TI and other manufacturers and that curve was not shown.

The main thing it shows is the output swing is greater to the positive supply than the negative direction for larger loads. This type of info is usually given with a different graph which does include large signal gain characteristics.

.
I see that now. Thanks.
I am reading "op amps for everyone" and the author Mancini shows other inconsistencies in the TL0xx datasheets I will be very careful in the future.
For your amusement here is a really weird datasheet:
**broken link removed**
Regards

 

[betwixt]

I like that data sheet :grin:
Specially the last two graphs which are truer than you might imagine!

Brian.