Analysis of the switching speed of BiCMOS buffer under high current

A nonlinear analytical transient response model that is suitable for BiCMOS driver circuits operating under the Kirk and Van der Ziel effect is presented. The model accounts for both base vertical push-out and lateral stretching phenomena where the forward transit time τ _f has a square law dependence on the collector current. Based on the new transient model, a closed-form BiCMOS delay expression is derived that shows excellent agreement with measured gate delay from a 0.8-μm BiCMOS technology. The comparison is made for a wide range of circuit parameters. The delay model can be used to develop timing analyzers, timing simulators, and circuit optimization tools for ULSI circuit design. As an application of the delay model, a circuit design algorithm is derived to optimize the speed-area performance of the BiCMOS buffers