Editing Operational amplifier (section)

=== Ideal op amps ===
[[Image:Op-Amp Internal.svg|thumb|250px|right|An equivalent circuit of an operational amplifier that models some resistive non-ideal parameters.]]

An ideal op amp is usually considered to have the following characteristics:<ref>{{cite web |url=http://www.ti.com.cn/cn/lit/an/slaa068b/slaa068b.pdf |title=Understanding Basic Analog – Ideal Op Amps |url-status=live |archive-url=https://web.archive.org/web/20161227060510/http://www.ti.com.cn/cn/lit/an/slaa068b/slaa068b.pdf |archive-date=2016-12-27 }}</ref><ref>{{cite web |url=http://research.cs.tamu.edu/prism/lectures/iss/iss_l5.pdf |title=Lecture 5: The ideal operational amplifier |url-status=dead |archive-url=https://web.archive.org/web/20161123045824/http://research.cs.tamu.edu/prism/lectures/iss/iss_l5.pdf |archive-date=2016-11-23 |access-date=2016-12-26 }}</ref><ref>{{Cite book |last=Schlaepfer |first=Eric |url=https://tubetime.us/wp-content/uploads/2018/10/Ideal-Op-Amp-Datasheet.pdf |title=IC01 Ideal Operational Amplifier |publisher=Perfect Semiconductor |year=2018 |access-date=2022-12-20}}</ref>

* Infinite [[open-loop gain]] ''G'' = ''v''<sub>out</sub> / ''v''<sub>in</sub>
* Infinite [[input impedance]] ''R''<sub>in</sub>, and so zero input current 
* Zero [[input offset voltage]] 
* Infinite output voltage range
* Infinite [[bandwidth (signal processing)|bandwidth]] with zero [[phase shift]] and infinite [[slew rate]] 
* Zero [[output impedance]] ''R''<sub>out</sub>, and so infinite output current range
* Zero [[Electronic noise|noise]]
* Infinite [[common-mode rejection ratio]] (CMRR)
* Infinite [[power supply rejection ratio]].
 
These ideals can be summarized by the two {{em|golden rules}}:
# In a closed loop the output does whatever is necessary to make the voltage difference between the inputs zero.
# The inputs draw zero current.<ref name=AoE>{{Cite book |last1= Horowitz |first1= Paul |last2= Hill |first2=Winfield |title= The Art of Electronics |publisher= Cambridge University Press |year= 1989 |location= Cambridge, UK |url= https://books.google.com/books?id=bkOMDgwFA28C&pg=PA177 |isbn=0-521-37095-7}}</ref>{{rp|177}}

The first rule only applies in the usual case where the op amp is used in a closed-loop design (negative feedback, where there is a signal path of some sort feeding back from the output to the inverting input).  These rules are commonly used as a good first approximation for analyzing or designing op-amp circuits.<ref name="AoE"/>{{rp|177}}

None of these ideals can be perfectly realized. A real op amp may be modeled with non-infinite or non-zero parameters using equivalent resistors and capacitors in the op-amp model. The designer can then include these effects into the overall performance of the final circuit. Some parameters may turn out to have negligible effect on the final design while others represent actual limitations of the final performance.