Editing 555 timer IC (section)

=== 558 quad timer ===
{{stack|[[File:Signetics Corporation NE558D 0136O07 9331KK KOREA.jpg|thumb|Die of a NE558 quad timer manufactured by [[Signetics]]]]}}
{{stack|[[File:NE558 pennen.svg|thumb|Pinout of 558 quad timer<ref name="Signetics_1985_Linear_Databook"/>]]}}
{{stack|[[File:NE558 intern.svg|thumb|558 internal block diagram. It is different from 555 and 556 timers.<ref name="Signetics_1985_Linear_Databook"/>]]}}

The quad version is called 558 and has four reduced-functionality timers in a 16-pin package designed primarily for [[monostable multivibrator]] applications.<ref>{{Cite book |last=Horn |first=Delton |title=Amplifiers, waveform generators, and other low-cost IC projects |publisher=TAB Books |year=1994 |isbn=0-07-030415-7 |location=New York |pages=27 |oclc=28676554 |quote=Not all functions are brought out to the 558's pins. This chip is designed primarily for monostable multivibrator applications}}</ref><ref name="Signetics_1985_Linear_Databook"/> By 2014, many versions of 16-pin NE558 have become obsolete.<ref name=":0">{{Cite book |last1=Platt |first1=Charles |url=https://books.google.com/books?id=FgRYBQAAQBAJ&pg=PT213 |series=Encyclopedia of Electronic Components |volume=2 |title=LEDs, LCDs, Audio, Thyristors, Digital Logic, and Amplification |last2=Jansson |first2=Fredrik |date=2014-11-13 |publisher=Maker Media |isbn=978-1-4493-3414-7 |language=en}}</ref>

Partial list of differences between 558 and 555 chips:<ref name="Signetics_1985_Linear_Databook"/><ref name=":0" />
* One ''V''<sub>CC</sub> and one GND, similar to 556 chip.
* Four "Reset" are tied together internally to one external pin (558).
* Four "Control Voltage" are tied together internally to one external pin (558).
* Four "Triggers" are falling-edge sensitive (558), instead of level sensitive (555).
* Two resistors in the voltage divider (558), instead of three resistors (555). 
* One comparator (558), instead of two comparators (555).
* Four "Output" are [[open-collector]] (O.C.) type (558), instead of [[Push–pull output|push–pull]] (P.P.) type (555).