A New Method for Calculating the Propagation Delay in CML Bipolar Switching

This paper introduces a new analytical method to predict the propagation delay in CML ring-oscillators. The gate delay in the fully optimized circuit is a figure of merit for evaluating switching performance of bipolar silicon processes. The expression found accounts for base resistance, base transit time, junction and diffusion capacitance effects and is reasonably simple and accurate. An extended formulation includes the effects of emitter and collector resistances. The analytical results are verified by time domain simulations of long ring-oscillators, as designed in different bipolar technologies.