This document describes simulation models provided by NXP for small-signal diodes and transistors and highlights specific features of the model architecture and the syntax used.

The Spice Gummel Poon (SGP) model is one of the oldest models published in 1970 by H.K. Gummel and H.C. Poon and has been standard for simulation of bipolar transistors and diodes for decades.

Though more accurate models are now available (e.g. HICUM, Mextram) the SGP model is still in great demand due to the availability of simulation software, partly as freeware.

NXP models for small-signal bipolar diodes and transistors are created by using the SGP model for use with the most conventional simulation software. Though models are optimized for use with the simulator software like PSpice or LTSpice, difficulties in applying the models cannot be excluded. In this case, please contact our customer support.

SGP provides a fast and cheap simulation with the advantage that high sophisticated calculating hardware is not necessary. However, when using SGP model, you have to be aware of the following characteristics:

• No simulation of junction breakdown
• Inadequacy of saturation area and dependence of RC on operating conditions. Especially in the area of quasi saturation, in some cases, less accuracy is archieved than by use of higher sophisticated models. To avoid larger deviations, NXP bipolar transistor spice models are optimized for the individual application range of each transistor type.
• Inaccuracy of hFE simulating in reverse mode of operation. This phenomen affects mainly PNP transistors with high breakdown voltages. To improve simulation results in this range, NXP models sometimes are created as subcircuit with additional devices.

Remark: The following explanations and comments refer to NXP small signal bipolar transistors and switching / Schottky diodes.