Emitter-coupled logic
high-speed integrated circuit bipolar transistor logic family
In electronics, emitter-coupled logic (ECL) is a high-speed integrated circuit bipolar transistor logic family. ECL uses a bipolar junction transistor (BJT) differential amplifier with single-ended input and limited emitter current to avoid the saturated (fully on) region of operation and the resulting slow turn-off behavior.
As the current is steered between two legs of an emitter-coupled pair, ECL is sometimes called current-steering logic (CSL),
current-mode logic (CML)
or current-switch emitter-follower (CSEF) logic.
In ECL, the transistors are never in saturation, the input and output voltages have a small swing (0.8 V), the input impedance is high and the output impedance is low. As a result, the transistors change states quickly, gate delays are low, and the fanout capability is high. In addition, the essentially constant current draw of the differential amplifiers minimizes delays and glitches due to supply-line inductance and capacitance, and the complementary outputs decrease the propagation time of the whole circuit by reducing inverter count.
ECL's major disadvantage is that each gate continuously draws current, which means that it requires (and dissipates) significantly more power than those of other logic families, especially when quiescent.
The equivalent of emitter-coupled logic made from FETs is called source-coupled logic (SCFL).
A variation of ECL in which all signal paths and gate inputs are differential is known as differential current switch (DCS) logic.
History
ECL was invented in August 1956 at IBM by Hannon S. Yourke.
This brief starts where responsible research should: with the source description of “Emitter-coupled logic” as high-speed integrated circuit bipolar transistor logic family. Everything that follows is an evidence route, not borrowed authority.
Why this record matters
The subject matters to the general reference register because the source frames it as high-speed integrated circuit bipolar transistor logic family. Its deeper value depends on whether names, dates, institutions and citations support that framing.
The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Jul 2, 2026. The linked authority identifier is Q173552. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1956.
A concise general-reference account can conceal disagreements about scope, terminology or the weight assigned to individual sources. The lead is largely declarative, so disagreement and counter-evidence require a deliberate search beyond the opening account. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Use the entry as an orientation point, then follow its citations and revision history. Names, dates and institutional relationships should be checked against the original record.
- Subject orientation
- Search vocabulary
- Locating named sources
The closest primary source, responsible institution and strongest cited specialist reference.
Three-step research path
- Establish the record: confirm the title “Emitter-coupled logic”, its source revision and the description used here.
- Expand the search: follow Emitter-coupled logic primary sources, Emitter-coupled logic archive and Emitter-coupled research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Emitter-coupled logic”?
- What terminology or title could unlock a more precise catalogue search?
- Which cited source is closest to the event, object or claim?
Search terms from this dossier
This entry incorporates text from “Emitter-coupled logic” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.