Editing Inverter (logic gate) (section)

===Performance measurement===
[[File:Inverter voltage transfer curve.png|thumb|300px|Voltage transfer curve for a 20 μm inverter fabricated at [[North Carolina State University]]]]

Digital inverter quality is often measured using the voltage transfer curve (VTC), which is a plot of output vs. input voltage. From such a graph, device parameters including noise tolerance, gain, and operating logic levels can be obtained.

Ideally, the VTC appears as an inverted step function – this would indicate precise switching between ''on'' and ''off'' – but in real devices, a gradual transition region exists. The VTC indicates that for low input voltage, the circuit outputs high voltage; for high input, the output tapers off towards the low level. The slope of this transition region is a measure of quality – steep (close to vertical) slopes yield precise switching.

The tolerance to noise can be measured by comparing the minimum input to the maximum output for each region of operation (on / off).

==== Linear region as analog amplifier ====
Since the transition region is steep and approximately linear, a properly-biased CMOS inverter digital logic gate may be used as a high-gain analog [[linear amplifier]]<ref>{{Cite web |orig-date=July 1973 |date=April 2003 |title=Application Note 88: CMOS Linear Applications |url=https://www.elektronik-kompendium.de/public/schaerer/FILES/an-88.pdf |website=[[National Semiconductor]]}}</ref><ref>{{Cite web |last=Stonier-Gibson |first=David |title=CMOS gate as linear amplifier |url=http://melbmcu.weebly.com/cmos-gate-as-analogue-amplifier.html |url-status=live |archive-url=https://web.archive.org/web/20220331092505/http://melbmcu.weebly.com/cmos-gate-as-analogue-amplifier.html |archive-date=2022-03-31 |access-date=2023-05-18 |website=Microcontroller Group, Moorabbin, Melbourne |language=en}}</ref><ref>{{Citation |title=CMOS Inverters as Analog Amplifiers (Adventures in Field Programmable Analog Arrays) | date=14 December 2021 |url=https://www.youtube.com/watch?v=DnO5sMU5DqU |access-date=2023-05-18 |language=en}}, Aaron Lanterman, Georgia Tech</ref><ref>{{Cite web |title=CMOS-Inverter-as-an-Amplifier {{!}} Analog-CMOS-Design {{!}}{{!}} Electronics Tutorial |url=https://www.electronics-tutorial.net/Analog-CMOS-Design/MOSFET-Amplifiers/CMOS-Inverter-as-an-Amplifier/ |access-date=2023-05-18 |website=www.electronics-tutorial.net}}</ref><ref>{{Cite web |title=Activity: CMOS Amplifier stages - ADALM2000 [Analog Devices Wiki] |url=https://wiki.analog.com/university/courses/electronics/electronics-lab-20 |url-status=live |archive-url=https://web.archive.org/web/20220808072638/https://wiki.analog.com/university/courses/electronics/electronics-lab-20 |archive-date=2022-08-08 |access-date=2023-05-18 |website=wiki.analog.com}}</ref> or even combined to form an [[opamp]].<ref>{{Cite web |last=Weltin-Wu |first=Colin |date=2013-11-18 |title=A true op-amp made from inverters |url=https://www.edn.com/a-true-op-amp-made-from-inverters/ |access-date=2023-05-18 |website=EDN |language=en-US}}</ref> Maximum gain is achieved when the input and output operating points are the same voltage, which can be biased by connecting a resistor between the output and input.<ref>{{Cite journal |last=Bae |first=Woorham |date=2019-09-20 |title=CMOS Inverter as Analog Circuit: An Overview |journal=Journal of Low Power Electronics and Applications |language=en |volume=9 |issue=3 |pages=26 |doi=10.3390/jlpea9030026 |doi-access=free |issn=2079-9268}}</ref>