Dylan Bartle

Improved breakdown voltage and hot-electron reliability PHEMT for high efficiency power amplifiers

By increasing the first recess width on the drain side of the gate, PHEMT breakdown was increased by as much as 5 V and hot electron RF stress was reduced by a factor of 2.5 to 3.5 with minor change in saturated power and power-added efficiency. Pulsed IV, loadpull and reliability measurement results are presented for PHEMT devices with various recess structures. The wide recess PHEMT provides necessary reliability margin for high efficiency and high mismatch operation of power amplifiers.

Electromagnetic only HEMT model for switch design

Electromagnetic (EM) only HEMT model has been proposed and realized with commercial available EM simulator. EM analysis has been applied, for the first time, to the intrinsic part of HEMT device. The small signal behaviors of HEMT can be accurately predicted based directly on the layout and process information. After introducing two EM HEMT models for HEMTs in both on and off states, entire switch circuit, as a whole, can be EM simulated. The prediction accuracy for switch performance can be remarkably improved by taking into account all of the distributed and coupling effects inside the circuit.

Multi-Gate pHEMT Modeling for Switch Applications

Multi-gate pHEMTs are extensively used in pHEMT switch circuits for wireless communication applications due to their size advantage. The intuitive modeling approach which considers a multiple-gate pHEMT to be a stack of single-gate FETs is far from adequate. Crucial factors in multi-gate pHEMT modeling include accurate leakage, CV below pinch-off, surface traps effects, and distribution features for large size switch FETs. In this paper we will address certain techniques to model both intrinsic FETs and extrinsic parasitic components. Our multi-gate pHEMT model was verified by comparisons of a variety of performances between modeled and measured data, including leakages, floating voltages, and CV curves on device level. In a switch application, comparisons of harmonics as a function of frequency at high driving power for both GSM and DCS bands show excellent agreement between model prediction and measured data as well.

Scaleable small-signal MESFET/PHEMT models up to 30 mm periphery

This paper addresses the issue of scaleability in equivalent-circuit based small-signal models for MESFETs and PHEMTs with periphery up to 30 mm. It is shown that large-periphery devices have complex distribution effects and the conventional scaling rule can be approximately applied only to certain elements in the equivalent circuit, namely Cgs, Cgd, Gm, and Gds. Modified scaling rules are proposed for devices with lager peripheries. The simulated S-parameters based on the new scaling rules give excellent fitting to the measured data.

Temperature dependent linear HEMT model extracted with multi-temperature optimization

Temperature dependent model is conventionally developed with 1) individual linear model extraction at each temperature and 2) temperature dependence extraction for each model parameter. A novel approach based on a multi-temperature optimization is proposed in this study. The new approach is faster and more accurate since the linear models at different temperatures are extracted simultaneously and inter-relatedly. It has been found, based on the model extracted, that there is a specific gate-source voltage of Vgs0, where the transconductance (Gm) keeps constant versus temperature. Gm increases (decreases) with temperature for Vgs<;Vgs0 (Vgs>;Vgs0). With increasing temperature, a substantial decrease in extrinsic inductance is also observed. Our findings are believed to be useful for designing HEMT amplifiers with less temperature dependence.

A comprehensive PHEMT core model for switch applications

A comprehensive non-linear PHEMT core model for switch applications is described. The model combines an accurate description of CV below pinch-off and a 2D CV function above pinch-off for better charge and capacitance modeling. At the same time, more accurate is the models IV prediction on the current in the near pinch-off region. The model has detailed leakage equations and dispersion function covering a wide range of operation, and taking gate lag into consideration. The model was verified by a variety of measured data, including IV/transfer curves, leakages, floating voltages and S-parameters/CV curves. In a switch application, comparison between modeled and measured data on harmonics, insertion loss and isolation regarding various driving power shows excellent and consistent agreement in both on-state and off-state.

Waveform characterization and modeling of dynamic charge behavior of InGaP-GaAs HBTs

This study presents a novel time-domain characterization method for the first time, to reveal dynamic charge behavior of HBTs. The charge model plays an important role in power InGaP-GaAs HBT amplifiers designed with self-biasing. It is shown that charge-storage and extraction from the base of the HBT at a high-power drive cannot be described by the conventional quasi-static model. A new collector-base charge model is proposed to account for the time-response of the devices.

Large-signal model of triple-gate MESFET/PHEMT for switch applications

A large-signal model of triple-gate MESFETs/PHEMTs is developed for switch applications. The devices are represented as multiple transistors connected in series. Systematic extraction procedure, including extrinsic parameters, is described. The model has been verified by comparing simulated dc characteristics, S-parameters and power performance of switches with measured results. As an example of applications, a feed-through circuit is simulated and preliminary experimental data supports the validity of the model.

Analysis, simulation, and measurement of envelope tracking linearization

Additional intermodulation distortions (IMD) are generated in an envelope tracking (ET) power amplifier (PA) due to the mixing between RF input and ET signals. ET linearization can thus be achieved by the IMD cancellation. Analytical expressions depicting the ET linearization mechanism are derived. IMD cancellation is demonstrated with a three tone harmonic balance simulation. Significant linearity improvement is experimentally observed with both two-tone and modulated signals.

Skyworks capacitor model for ESD applications

The Skyworks Capacitor model for ESD applications is described and discussed. A Skyworks ESD Capacitor is modeled as an ideal capacitor in parallel with a leakage current source, along with a resistor to the ground modeling the substrate leakage at each terminal. The current-voltage and small-signal characteristics predicted by the model coincide with measurement results. Furthermore, by employing the Human-Body Model (HBM), an ESD simulation environment is set up in order to simulate ESD tests on Skyworks ESD Capacitors. The breakdown criteria of two kinds of Skyworks ESD Capacitors are investigated and the corresponding model is investigated and developed based on experimental data.