i want to build a circuit that expands dc range

How much power or current does it need to supply? (at 5V)

This chip gets down to 0.7 V....

https://www.ti.com/lit/ds/symlink/tps61098.pdf?ts=1715554368492

But it is tough to build it on a Vero board.

There are lots of ways this could be done but none are perfect. You need to tell us what the source of the signal is and where its going.

The more you explain the context the better the answer you will get. The information you have provided so far isn't quite enough to make any good suggestions.

MK

THE OUTPUT from this is going into a DAQ unit that i don,t have info for so output current would be minimal 

this is feed into a computer program which can do automatic calibration 

but when the calbration is used the input limits drift which will eventually crash the program 

so i set this up using a external pot  and worked for 3 hours no problem before i shut it down 

so i think with dual op amp ic and twin rail i should get to 0v min 

You could try a joule thief circuit.....

https://www.youtube.com/watch?v=nBn4JEvv93c&ab_channel=HowDoYou%3FDIY

https://www.youtube.com/watch?v=K53beWYdIpc&ab_channel=bigclivedotcom

I'm guessing the OP wants to condition a signal with Vo = a + bVin, but not sure...

Unfortunately, this still needs a lot more information. Unless you're fully open about the actual use-case, and provide as much detail as possible about what this is for, it's near-impossible to help. The original information was extremely minimal, this is currently only fractionally better.

If you really think you need an op-amp circuit then you can plug the values into an online calculator and get a circuit: https://masteringelectronicsdesign.com/differential-amplifier-calculator-2/

However, whether that will actually provide a real solution or not, I have no idea, because the information isn't there.

Why did it stop working correctly?

The way I interpret your setup is as follows:

You are using a circuit to calibrate a DAQ instrument.

Ideally you would like this 'stimulus circuit' to operate from 0V to 2.5V.

Unfortunately instead of 0V, the stimulus circuit only goes down to 0.48V.

My comments:

If your stimulus circuit has an op-amp  ensure that it is a rail to rail type, or look to using a negative rail as you suggest in your later post.