Dynamic push-pull for ECL

摘要

An improved ECL gate having faster output transition times without requiring additional current is provided. Two switching transistors have their emitter terminals connected to a first current source. A reference switching transistor has its base connected to a reference voltage and an input switching transistor has its base connected to an input terminal. An emitter follower transistor is coupled to each switching transistor. A second current source is connected to each of the emitter follower transistors by coupling circuitry which shunts current from one emitter follower to the other thereby increasing the transition speed of the outputs. In the preferred embodiment, the emitters of the current source transistors for the two outputs are coupled through a common resistance to ground. The collector of the inverting emitter-coupled transistor is coupled via a capacitor to the base of the current source transistor for the non-inverting output. The collector of the non-inverting emitter-coupled transistor is coupled via a second capacitor to the base of the current source transistor for the inverting output. The base of each such current source transistor is coupled to a current source voltage via a resistance or a diode. The capacitance coupling essentially causes only one of such current source transistors to be turned on at any one time during switching. This forces all the current through one or the other of the current source transistors, thus allowing the output which requires such current to change states faster.