IVCAD Suite Modeling

A compact transistor model is an equivalent representation of different elements that describes the physical phenomena occurring in the component to accurately simulate the linear and nonlinear behavior of the component.

Unlike a pure black box mathematical model, a compact model is inspired by the physical phenomena of semiconductors through an equivalent diagram composed of linear elements (resistors, capacitors, inductors) and non-linear elements (current sources, diodes, capacitors), represented using mathematical equations in order to mimic the behavior of the transistor.

Once the model is able to fit the pulse Voltage & Current characteristics, it is essential to upgrade this one with a thermal circuit that represents its dynamic self-heating behavior.

In RF transistors, the dissipated power depends on the operating conditions (e.g., bias point, signal power, frequency). This power causes a rise in junction temperature. For high-signal (high-power) operation, the power dissipation is usually calculated from the dynamic characteristics of the device.

This self-heating is particularly important when considering the impact of thermal effects on performance at higher power levels. For small signals, power dissipation is typically related to the quiescent current (IDQ) and operating voltage (VDQ). For large signals, the instantaneous power dissipation depends on the input signal, requiring timing analysis or integration of the device power over the signal period.

IVCAD (IVM) offers a turnkey solution for modeling thermal phenomena for each of the model’s parameters in order to introduce a dynamic temperature dependence.

Trapping effects in GaN (Gallium Nitride) transistors, especially in high-power and high-frequency applications, can significantly affect the transistor's performance. These effects occur due to the trapping and de-trapping of charge carriers in the semiconductor material or at the interface between different layers in the device.

Trapping can lead to issues like dynamic threshold voltage shifts, transient effects, and degraded switching behavior, all of which are critical for accurate RF transistor modeling. To extract a GaN transistor model that accounts for trapping effects, you need to carefully characterize the device using time-dependent measurements and incorporate these effects into your compact model.

Once the current source model is developed, other elements of the model such as nonlinear capacitances and diodes must be extracted to simulate the actual behavior of the component under different operating conditions as a function of temperature, frequencies, bias voltages, and source and load impedances.

The compact model must account for the variation of output power and efficiency as a function of load impedance, as this is the core of load-pull simulations for a reliable circuit design process based on this model.

To achieve an accurate fit to nonlinear load-pull measurements in a compact transistor model, several key model elements must be carefully addressed. The model must capture the nonlinearities due to these high-power signal conditions.

IVCAD (IVM) allows optimization of multiple model parameters to fit load pull data without degrading IV and S parameter simulations by refining the current source model, nonlinear capacitances, memory plus thermal effects, and bias-dependent parameters.

IVCAD (IVM) does enable the export of transistor compact models to third-party circuit simulators.

While IVCAD provides a set of tools to extract, calibrate, and refine compact models for these GaN, GaAs and LDMOS devices, such models can be exported to various third-party circuit simulators. The software enables the export of transistor compact models to third-party circuit simulators.

File Formats: IVCAD (IVM) usually exports models in common formats such as Netlists that can be read by most circuit simulators. This export process allows seamless integration of the generated transistor model into a broader simulation environment where the performance of the transistor can be analyzed in larger circuit contexts.

Interfacing:  IVCAD (IVM) software has direct support for integration with these simulators and provides specific tools for the correct setup of the exported models, such as ensuring that model parameters and component connections are properly mapped to the third-party simulation environment.

Extracting a transistor model generally requires skills, time, and various types of measurements, which can make this process unaffordable when the time and budget of the amplifier design team's are limited. Behavioral models are useful in several applications : to hide the details of the transistor specifics while concentrating on its performance and response, to improve the speed of simulation or to model a packaged component.

IVCAD Suite Modeling permits to use large signal data provided by the  IVCAD Measurement Suite Specialized (IVZ) to extract a transistor model from these measurements that can reproduce the transistor behavior during a Harmonic Balance simulation. Models can allow interpolation or extrapolation of the transistor performance for different matching conditions and various harmonic load impedances.

This model can be parametric, meaning it can be extracted for different bias, temperatures and frequencies, to cover the operating conditions required for simplified design of the final circuit.