In a given process run ("batch") they'll be the same. Next "batch",
probably could differ by as much as a volt.
This reminds me an old (12 years or so) design of mine, where I
needed variable gain cells, DC to say 10 MHz, 12 bit, 1:50 factor or
so.
I used paired 2N4391-s; one for compensation feedback, the other
as a variable resistor (having the gates shorted was handy as
it allowed me to solder the cans together for temperature coupling).
Buying about a 100 transistors inevitably bought me most if not
all of them from the same wafer and I could find decent pairs
easily enough.
Now obviously I did not get 12-bit temperature stability, but I had
anticipated this sort of trouble and had put an AD792 temperature
sensor next to them
. I had an MCU and it did turn the fine gain
to compensate; this gave me a 10x+ advantage over competitors
(who were _awarded_ all major deals in spite of that, but that's
another story).
Now the rest of the story is that I got no 12-bit integral non-
linearity,
either. Obviously even the 4391, in the reasonable low-voltage
range where I used it, was about 0.5 to may be 1% non-linear,
which was not acceptable. Fortunately I had enough processing
power (on a 16.67 MHz 68340
to acquire the non-linear
data into a somewhat longer spectrum (8192 was the norm;
I did something like 8500 or so) and continuously (IIRC 10 times
a second) converted it down to a linearized version.... Worked
wonderfully, some are still in use.
Got carried away by just a phrase, I guess, but I see this
as a "heroic" design of mine (there are more reasons except
the above for me to think so
and I felt like telling about it
although being only very remotely related to the context...
Dimiter