Emitter-coupled logic
![Motorola ECL 10,000 basic gate circuit diagram[1]](/uploads/202501/25/ECL.svg3106.png)
![Yourke's current switch, c. 1955.[9]](/uploads/202501/25/CurrentSwitchLogic.svg3106.png)

In electronics, emitter-coupled logic (ECL) is a high-speed integrated circuit bipolar transistor logic family. ECL uses an overdriven BJT differential amplifier with single-ended input and limited emitter current to avoid the saturated (fully on) region of operation and its 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.