An ABT model for InP-based single HBT's (SHBT's) was developed based on the conventional Gummel-Poon large-signal BJT model available in HSPICE. Several typical characteristics observed from InP-based SHBT's, such as soft breakdown and collector transit-time delay effects, were modeled through a macro modeling approach. Excellent agreement has been achieved between the experimental and calculated results based on the model.