A broadband current sensor based on the X-Hall architecture

A broadband current sensor, which is fully integrated and galvanically-isolated, is presented in this paper. The current sensor relies only on a Hall-effect probe to realize the magnetic sensing core so as to minimize the cost and the occupied space. Bandwidth limitations of state-of-the-art Hall-effect probes are overcame by combining the novel X-Hall architecture with a wide bandwidth differential-difference current-feedback amplifier. A prototype implemented in 0.16 \u3bcm BCD technology demonstrates a bandwidth wider than 20 MHz. Offset, sensitivity and power consumption are comparable to the state of the art. This is the first Hall-only current sensor achieving a bandwidth higher than 3 MHz

Charge-conservative GaN HEMT nonlinear modeling from non-isodynamic multi-bias S-parameter measurements

Guaranteeing charge conservation of empirically extracted Gallium Nitride (GaN) High-Electron-Mobility Transistor (HEMT) models is necessary to avoid simulation issues and artifacts in the prediction. However, dispersive effects, such as thermal and charge-trapping phenomena, may compromise the model extraction flow resulting in poor model accuracy. Although GaN HEMT models should be extracted, in principle, from an isodynamic dataset, this work deals with the systematic identification of an approximate, yet most suitable, charge-conservative empirical model from standard multi-bias S-parameters, i.e., from non-isodynamic data. Results show that the obtained model maintains a reasonable accuracy in predicting both small- and large-signal behavior, while providing the benefits of charge conservation

Efficient implementation of a modified-Volterra radio-frequency power amplifier nonlinear dynamic model by global rational functions approximation

Power amplifiers (PAs) used in modern radio frequency transmitters for communications display significant nonlinear dynamic effects under typical operating regimes. Accurate and efficient implementations of behavioral models describing these effects are required in order to enable system-level simulation, or for guiding the design of effective linearization predistorters. This work proposes an efficient implementation of the widely adopted modified-Volterra model, resulting from a global rational functions approximation of the model nonlinear convolution kernels. The proposed implementation, tested by gallium nitride PA simulations, reproduces the model behavior with high-accuracy and features an extremely compact structure, comparing favorably with alternative descriptions

Assessment of the Trap-Induced Insertion Loss Degradation of RF GaN Switches under Operating Regimes

It is well known that the trap-induced performance degradation of microwave GaN-on-SiC HEMTs is proportional to the peak voltages applied at the device's terminals. Considering that RF GaN switches are subject to high voltages, their characteristics are especially affected by trapping phenomena. This paper describes the GaN switch insertion loss (IL) degradation due to traps. A custom characterization setup is used for the measurement of the switch IL under dynamic voltage stress, typical of the actual operating regime. It is shown that, depending on the applied voltages setting the trap state, an increase of the switch IL up to 60% was measured for a 0.25 \u3bc m GaN-on-SiC technology

Experimental Characterization of Charge Trapping Dynamics in 100-nm AlN/GaN/AlGaN-on-Si HEMTs by Wideband Transient Measurements

This article deals with the characterization of charge trapping dynamics in a novel 100-nm double-heterojunction AlN/GaN/AlGaN-on-Si radio frequency (RF) HEMT process. In order to study the detrapping mechanisms, we perform the wideband acquisitions of the transient behavior by sweeping the pulsed voltages to cover the entire device operating area. The fast acquisition also enables the characterization of the charge capture behavior, a key aspect for RF performance. From the analysis of the drain current transients, time constants are extracted, showing a fundamental release time constant in the order of 0.1-1 ms, and more than one capture constants, the fastest being in the order of 300 ns. To the best of authors' knowledge, this is the first time that trapping dynamics under large-signal regime are characterized for this type of process

Broadband error vector magnitude characterization of a GaN power amplifier using a vector network analyzer

This work investigates the impact of nonlinear dynamic effects due to charge trapping and other long-memory phenomena on the wideband linearity of power amplifiers (PAs) for 5G communications applications. The proposed method uses the well-known best linear approximation framework (BLA) to estimate the error vector magnitude (EVM) of the amplifier for the class of modulated signals sharing the same probability density function (pdf) and power spectral density (PSD) as the 5G waveform standards. The dependency of the EVM and the BLA on the large-signal operating point (LSOP) of the PA is studied using random phase multisine signals belonging to the same class. In particular, we evaluate the impact of different signal repetition periods in order to excite low-frequency dynamic phenomena across a wide range of time scales. Results, using just standard vector network analyzer (VNA) relative measurements, are reported for a Gallium Nitride (GaN) power amplifier (PA) for two different 5G-FR1-compliant bandwidths of 20 and 100 MHz around 5.5 GHz

Microwave Characterization of Trapping Effects in 100-nm GaN-on-Si HEMT Technology

Trapping effects of a state-of-the-art 100-nm GaN-on-Si high-electron mobility transistor (HEMT) process for radio-frequency (RF) applications are characterized for the first time. Considering an operation with high peak-to-average power ratio (PAPR) signals, pulsed-RF measurements give a more direct understanding of the dynamic trap behavior than the third-order intermodulation products (IM3). The experimental data are used for estimating the time constants describing the transients in the presence of signals with different PAPRs

Narrow-pulse-width double-pulsed S-parameters measurements of 100-nm GaN-on-Si HEMTs

GaN HEMT dispersive phenomena due to charge trapping can be effectively characterized by means of pulsed IV measurements. In this work, we exploit the wideband feature of the setup obtaining pulsed S-parameters measurements within narrow pulse widths, in the order of a few hundred ns. Then, we report the single and double-pulsed S-parameters characterization of the 100-nm GaN-on-Si HEMT technology by OMMIC, showing the impact of traps on the small-signal parameters and providing significant data for compact model identification

VNA-based broadband EVM measurement of an RF nonlinear PA under load mismatch conditions

In the context of modern communications systems operating at radio-frequency (RF), the error vector magnitude (EVM) is the most commonly adopted metric to quantify modulation distortion caused by a nonlinear device. While EVM is typically measured with instrumentation featuring broad acquisition bandwidth (BW), here we implement a method based on multiple narrowband vector network analyzer (VNA) acquisitions, allowing for improved measurement accuracy and for broader characterization BWs. We report the EVM characterization of a nonlinear RF power amplifier (PA), analyzing, in particular, the case of the PA cascaded with a linear network, under load mismatch conditions as imposed by a narrowband passive tuner

A bias network for small duty-cycle fast-pulsed measurement of RF power transistors

Radio-frequency power transistors affected by dispersive phenomena such as thermal and charge trapping effects can be effectively characterized and modeled by means of pulsed current-voltage measurements. This work presents the design of a passive bias network made out of off-the-shelf components and tailored for the application of fast pulses through its capacitive path, yet extending the bandwidth down to a few kHz. This custom component enables small duty-cycle (e.g., 0.1 %) fast-pulsed excitations of several tens of V of ac voltage in the presence of bias voltages up to 50 V and bias currents up to 2 A