A Self-Biased Feedback-Controlled Pull-Down Emitter Follower for High-Speed Low-Power Bipolar Logic Circuits

A feedback-controlled active-pull-down emitter follower that is self-biased at a low steady-state current and allows the collector dotting and emitter dotting is proposed for high-speed low-power bipolar/BiCMOS digital logic circuits. The push-pull operation of this emitter follower is precisely controlled by a feedback mechanism and does not require any extra out-of-phase signal other than the emitter-follower input from the logic stage. Simulation results based on a 0.5-µm advanced Si-bipolar technology show that the pull-down delay and drive capability of a loaded 1-mW feedback-controlled pull-down ECL gate are improved to the pull-up levels, 2.7 and 10 times better than those of the conventional resistor-pull-down ECL circuit, respectively. © 1994 IEEE