High-Frequency BJT (Gummel-Poon) Model

The Agilent 85193A high-frequency BJT model is a three-terminal version of the Gummel-Poon model, with a measurement and extraction methodology that has been developed specifically for high-frequency devices.

The high-frequency BJT model provides improved accuracy for modeling the AC parameters of a high-frequency device, by using a network analyzer to measure the device S-parameters. Additionally, because accurate capacitance measurements are extremely difficult at high frequencies, the software computes the model junction capacitances from the measured S-parameter data, rather than using a CV meter.

This chapter provides example procedures to enable you to use the software as a tool to measure your devices and extract their model parameter values. They take you step-by-step through a BJT measurement and parameter extraction. The procedures are arranged in the most logical sequence to allow earlier measured data or extracted parameters to be used as a basis for later measurements or extractions. The sequence also requires the least number of configuration changes.

The procedures use a series of different setups to measure current or voltage versus bias under different bias conditions. The measured values are later used in the extraction process to isolate individual parameters. In the BJT model, the parameters are very interdependent because of the inherent coupling of the model equations. The purpose of the different measurement setups is to decouple the SPICE equations as much as possible.