Editing Electronics (section)

== Types of circuits ==
Electronic circuit functions can be divided into two function groups: analog and digital. A particular device may consist of circuitry that has either or a mix of the two types. Analog circuits are becoming less common, as many of their functions are being digitized.

=== Analog circuits ===
{{Main|Analog electronics}}
[[Analog circuits]] use a continuous range of voltage or current for signal processing, as opposed to the discrete levels used in digital circuits. Analog circuits were common throughout an electronic device in the early years in devices such as radio receivers and transmitters. Analog electronic computers were valuable for solving problems with continuous variables until digital processing advanced.

As semiconductor technology developed, many of the functions of analog circuits were taken over by digital circuits, and modern circuits that are entirely analog are less common; their functions being replaced by hybrid approach which, for instance, uses analog circuits at the ''front end'' of a device receiving an analog signal, and then use digital processing using [[microprocessor]] techniques thereafter.

Sometimes it may be difficult to classify some circuits that have elements of both linear and non-linear operation. An example is the voltage comparator which receives a continuous range of voltage but only outputs one of two levels as in a digital circuit. Similarly, an overdriven transistor amplifier can take on the characteristics of a controlled [[switch]], having essentially two levels of output.

Analog circuits are still widely used for signal amplification, such as in the entertainment industry, and conditioning signals from analog sensors, such as in industrial measurement and control.

=== Digital circuits ===
{{Main|Digital electronics}}
Digital circuits are electric circuits based on discrete voltage levels. Digital circuits use [[Boolean algebra]] and are the basis of all digital computers and microprocessor devices. They range from simple logic gates to large integrated circuits, employing millions of such gates.

Digital circuits use a [[binary system]] with two voltage levels labelled "0" and "1" to indicated logical status. Often logic "0" will be a lower voltage and referred to as "Low" while logic "1" is referred to as "High". However, some systems use the reverse definition ("0" is "High") or are current based. Quite often the logic designer may reverse these definitions from one circuit to the next as they see fit to facilitate their design. The definition of the levels as "0" or "1" is arbitrary.<ref>{{cite book |last1=Brown |first1=Stephen |last2=Vranesic |first2=Zvonko |title=Fundamentals of Digital Logic|format=e-book |date= 2008 |publisher=McGraw Hill |isbn=978-0077144227 |url=https://books.google.com/books?id=8oVvEAAAQBAJ&dq=what+do+0+and+1+mean+in+binary+arbitrary+high+voltage&pg=PA78 |language=en |access-date=12 August 2022 |archive-date=4 October 2022 |archive-url=https://web.archive.org/web/20221004155236/https://www.google.com/books/edition/EBOOK_Fundamentals_of_Digital_Logic/8oVvEAAAQBAJ?hl=en&gbpv=1&dq=what+do+0+and+1+mean+in+binary+arbitrary+high+voltage&pg=PA78&printsec=frontcover |url-status=live }}</ref>

[[Ternary computer|Ternary]] (with three states) logic has been studied, and some prototype computers made, but have not gained any significant practical acceptance.<ref name="AoCP2">{{cite book |last=Knuth |first=Donald |title=The Art of Computer Programming |volume=2: Seminumerical Algorithms |pages=190–192 |publisher=Addison-Wesley |edition=2nd |date=1980 |isbn=0201038226|title-link=The Art of Computer Programming }}.</ref> Universally, [[Computer]]s and [[Digital signal processor]]s are constructed with [[Digital data|digital]] circuits using [[Transistor]]s such as [[MOSFET]]s in the electronic logic gates to generate binary states.
[[File:Logic-gates-circuits.png|thumb|A selection of logic gates, used extensively in digital electronics]]
* [[Logic gate]]s
* [[Adder (electronics)|Adders]]
* [[Flip-flop (electronics)|Flip-flops]]
* [[Counter (digital)|Counters]]
* [[Processor register|Registers]]
* [[Multiplexer]]s
* [[Schmitt trigger]]s

Highly integrated devices:
* [[Memory chip]]
* [[Microprocessor]]s
* [[Microcontroller]]s
* [[Application-specific integrated circuit]] (ASIC)
* [[Digital signal processor]] (DSP)
* [[Field-programmable gate array]] (FPGA)
* [[Field-programmable analog array]] (FPAA)
* [[System on chip]] (SOC)