ECL Gate with switched load current source

摘要

A standard ECL OR/NOR gate is modified to have a single current source connected to the load current source transistors. The single current source is connected to the emitters of each of the load current source transistors. Switching between the two load current source transistors is accomplished by connecting the base of at least one of the load current transistors to a circuit point that tracks the opposite phase. In one embodiment the base of one of the load current source transistors is connected to the common emitter connections of the input transistors and the reference transistor while the base of the other load current source transistor is connected to a reference voltage source VBBL having a value intermediate the extreme values which appear on the common emitter connections of the input transistors and the reference transistors. In an alternate embodiment the base of each load current source transistor is connected to a suitable point which tracks the opposite phase outputs of the particular load current source transistor.