
NMOS IC Reverse Engineering (2017) - userbinator
https://www.wdj-consulting.com/blog/nmos-sample.html
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kurthr
Although CMOS FETs now completely dominate the (mostly digital) crystal Si
wafer manufacturing, simple NMOS and PMOS are still predominantly used in the
display industry. They are different because the TFT substrate (usually glass)
is of course non-conductive so there is no "body effect" of a surrounding P/N
well.

Both a-Si (amorphous) and poly-Si (poly crystalline) dominate their respective
TFT (thin film transistor) manufacturing technologies. For large scale
displays (TVs) a-Si is typically used due to lower cost structure (no laser
crystal annealing of the poly) while for smaller displays (mobile devices)
LTPS (low temp poly-Si) is used due to higher mobility (smaller transistors).
Typically NMOS is used for poly and a-Si (again for mobility reasons)...
interestingly there is relatively little CMOS TFT manufacturing.

Due to layer stack-up and processing yield for mobile OLED, PMOS LTPS is
dominant there (both for rigid and flexible). That makes analyzing the
relatively simple (2-3 metal) and larger geometry (2-3um) layouts of displays
so easy and interesting for an amateur... the challenges are in figuring out
all of the parasitic couplings and layout constraints that drive their design.
Conveniently, old displays are free and easy to get and relatively simple
(compared to de-capping a plastic package) to deconstruct and examine with a
cheap microscope. Figure out how that high resolution flashing light box
really works!

~~~
userbinator
_Due to layer stack-up and processing yield for mobile OLED, PMOS LTPS is
dominant there_

In the late 60s/early 70s, PMOS was also dominant because it was less affected
by impurities than NMOS. The quite common LM8560 alarm clock IC was an example
of early PMOS and is apparently still in production today. A distinguishing
characteristic is the odd negative supply voltage.

[http://www.decodesystems.com/clock-
ics.html](http://www.decodesystems.com/clock-ics.html)

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eternauta3k
Very interesting. He could do this in KLayout instead of Inkscape, and have
access to EDA tools to check connectivity and other things.

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ruslan
I wonder why this guy was trying to look at ROM inputs as binary bus trying to
figure a truth table. AFAIK, they are selection lines from decoder, hence only
one of the lines can be active at a time, i.e. depicted ROM is only 5 words of
10 bits each.

