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Comparison of Measured (symbols) and simulated (lines) results with different input powers at 14 GHz.
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This paper presents a large-signal empirical model for GaN HEMT devices using an improved Angelov drain current formulation with self-heating effect and a modified non-linear capacitance model. The established model for small gate-width GaN HEMTs is validated by on-wafer load-pull measurements up to 14 GHz. Moreover, a scalable large-signal model i...
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Citations
... Based on Angelov model, many literatures have been proposed to improve the modeling of GaN HEMT. [11][12][13] Furthermore, in References 14,[18][19][20] dispersion effects such as self-heating effect and trapping effect are incorporated into the large-signal model, which leads to a better prediction of large signal performance. Advanced measurement techniques have been proposed for properly characterizing the thermal and trapping effects of GaN HEMTs. ...
... Advanced measurement techniques have been proposed for properly characterizing the thermal and trapping effects of GaN HEMTs. 21,22 Several scalable large-signal models with self-heating effect are developed, [10][11][12][23][24][25] and most models have realized the scalability by adding linear scaling factors to the equivalent circuit parameters and empirical drain-source current formula. However, the accuracy of the scalable model may be reduced as the gate-width of GaN HEMT devices increases. ...
In this paper, a novel hybrid‐scaling rule for GaN high‐electron‐mobility transistors (HEMTs) scalable large‐signal model with self‐heating effect is proposed. Due to the complex parasitic characteristics of large gate‐width GaN HEMT devices, nonlinear scaling rules are used to consider the dependence of the extrinsic inductances, extrinsic resistances, and thermal resistance on the gate width. In addition, a drain‐source current model and gate capacitance models are proposed to improve the accuracy of traditional Angelov model. A one stage resistor‐capacitor network is attached in the current model to characterize self‐heating effect. Therefore, a scalable large‐signal model based on a hybrid‐scaling rule is presented for the first time. Compared with traditional linear scalable model, the proposed model has a good prediction for multi‐bias S‐parameters and direct current (DC) I‐V curves of different size devices, and can also significantly improve the fitting degree of S22 parameter at high frequency. Moreover, the proposed scalable model shows a good prediction of large‐signal characteristics for large size GaN HEMT devices.
... Large-signal models (LSMs) form a bridge between the device and the circuit and have been used in SPICE-like commercial microwave electronic design automation software. 6 Typically, LSMs can be categorized as either empirical models (i.e., Angelov models [6][7][8][9][10] or physics-based models (i.e., ASM-HEMT 5,[11][12][13]. Over the past decade, significant research efforts have focused on GaN HEMT equivalent-circuit modeling 12,[14][15][16] and parameter-extraction methods. ...
... Large-signal models (LSMs) form a bridge between the device and the circuit and have been used in SPICE-like commercial microwave electronic design automation software. 6 Typically, LSMs can be categorized as either empirical models (i.e., Angelov models [6][7][8][9][10] or physics-based models (i.e., ASM-HEMT 5,[11][12][13]. Over the past decade, significant research efforts have focused on GaN HEMT equivalent-circuit modeling 12,[14][15][16] and parameter-extraction methods. ...
... Based on traditional empirical models, QPZD models use the linear-scaling rules to scale parasitic and intrinsic parameters. 6,9,32,33 Compared with the traditional scaling model, the model proposed herein adds thermal considerations, which improves the accuracy of the model. ...
A scalable eletrothermal model is necessary for a high‐power amplifier design for accurate accounting of thermal effects. Toward this end, this study presents a scalable large‐signal model of gallium‐nitride (GaN) high‐electron‐mobility transistors (HEMTs) on diamond substrates. First, a three‐dimensional (3D) thermal analysis model was established. Then, a modified eletrothemal expression was proposed to predict thermal effects including scalability. For validation, the proposed model was implemented into quasi‐physics zone division (QPZD) large‐signal model. Results show that the proposed model accurately predicts the I–V curves of devices with different gate widths, gate fingers, and ambient temperatures. Moreover, the results of the model are consistent with on‐wafer measurements of 2 × 125, 4 × 125, and 10 × 50 μm of GaN‐on‐diamond HEMTs, indicating that the proposed model accurately predicts the DC–IV curves, scattering parameters, and large‐signal performance. The findings of this study can be useful for designing microwave diamond–GaN HEMT circuits.
... (iii) ECP provides an assistance to explore the device performance even beyond microwave measurement framework. Apart from these advantages, the small-signal model has its own limitation, it is useful only under the small-signal condition at the set DC biasing points, but it can be used as the starting point to evaluate both noise and large-signal model [16][17][18][19][20][21][22]. ...
An improved parasitic resistance extraction from small-signal equivalent-circuit and effect of C ds in GaN HEMTs is presented. Parasitic capacitances are evaluated at ‘cold pinch off’ condition. More accurate extraction method of parasitic resistance is presented at low gate bias voltages compared to earlier published work. The impact of drain to source capacitance (C ds ) at low gate bias voltage is also reported in this manuscript. The validity of proposed parasitic resistance extraction procedure and effect of drain to source capacitance (C ds ) has been verified through error analysis with the measured S-parameters data of 0.8- μ m of AlGaN/GaN high electron mobility transistor consisting 2 × 200- μ m gate width. Proposed method shows good harmony between simulated and measured data up to 40 GHz frequency.
... [8][9][10] Empirical models have been widely used because they are more flexible and easier to simulate. 11,12 The accuracy of empirical models is heavily dependent on the measured data, 13 including I-V characteristics, S-parameters, and thermal effects. To get precise and sufficient measured data of transistors, one needs to ensure appropriate and reasonable measurements. ...
... In traditional method, the drain-source current model of the 3.6 mm device is always obtained by exploiting the scaling rules. 12 With a reference device of 0.8 mm AlGaN/GaN HEMT, the scaling model of the 3.6 mm device can be obtained. The comparison of the measured and simulated pulsed I-V of the 0.8 mm model is shown in Fig. 19, which are in good agreement. ...
Measurement for modeling of the high-power transistors is difficult due to its high-power and low-impedance characteristics. In this paper, novel methods and devices were designed and applied to achieve precise measurements of the high-power transistors. Fixtures capable of withstanding high voltage and current were designed to replace traditional radio frequency (RF) probes for higher power capacity. To reduce the impact of capacitive and inductive components of traditional bias tees on the rising/falling edge, two wideband 90° hybrid couplers that were connected back-to-back were designed for pulsed measurements. The measurement system of stable S-parameters with the Vector Network Analyzer (VNA) was reported, which could protect the devices and laboratory equipment from damage of self-oscillation. Application of several innovative approaches enabled accurate I–V characteristic and S-parameters measurements of high-power transistors in DC or pulsed mode. Experimental results of a 30 W gallium nitride high-electron-mobility transistor verified the validity.
... Especially for power amplifiers (PAs), the related characteristics such as bandwidth and efficiency must be greatly improved. Recently, many high-efficiency RF PAs have been reported in [3][4][5][6][7][8][9][10][11]. The traditional harmonic control PAs such as Class F PAs [12][13][14][15] and switch PAs like the class E PAs [16][17][18][19] have became the research hotspots because of their ideal 100% of drain efficiency. ...
This paper proposes a broadband Class EF power amplifier based on a low-pass filter matching structure. Based on the theory of Class EF power amplifiers, the optimal fundamental load impedance required is derived. A broadband matching circuit is then designed using a low-pass filter prototype. In the meantime, a compact harmonic control circuit is proposed to meet the harmonic impedance requirements of class EF power amplifiers. In order to validate the effectiveness of the proposed method, a 2.6-3.6 GHz broadband class EF power amplifier is designed and fabricated. Measurement results show that the output power is between 40.68 dBm and 41.6 dBm at 1 dB compression point in 2.6-3.6 GHz. From 62% to 78% of drain efficiency is obtained with a gain greater than 10 dB.
... During the past years, many large-signal models for GaN HEMTs in different types were developed to characterize their large-signal behavior [12][13][14][15]. However, high modeling accuracy can be considered to be quite close to be guaranteed in the academic world, but still far away from being accessible to circuit designers. ...
... 15: Measured (symbols) and modeled (lines) I ds and g m of the 250 µm GaN HEMT, described by the Chalmers current model. ...
... 15 shows large-signal model predictions of I ds and g m together with the ...
Although GaN HEMTs are regarded as one of the most promising RF power transistor technologies thanks to their high-voltage high-speed characteristics, they are still known to be prone to trapping effects, which hamper achievable output power and linearity. Hence, accurately and efficiently modeling the trapping effects is crucial in nonlinear large-signal modeling for GaN HEMTs. This work proposes a trap model based on an industry standard large-signal model, named Chalmers model. Instead of a complex nonlinear trap description, only four constant parameters of the proposed trap model need to be determined to accurately describe the significant impacts of the trapping effects, e.g., drain-source current slump, typical kink observed in pulsed I/V characteristics, and degradation of the output power. Moreover, the extraction procedure of the trap model parameters is based on pulsed S-parameter measurements, which allow to freeze traps and isolate the trapping effects from self-heating. The model validity is tested through small- and large-signal model verification procedures. Particularly, it is shown that the use of this trap model enables a dramatical improvement of the large-signal simulation results.
... The characterization of scalability is an indispensable step in the development process of a compact model. Up to now, scalable models of multiple fingers or multiple cells devices have been widely investigated [21]- [23]. By performing the full-wave electromagnetic analysis, the accurate parasitic effects are obtained of the actual device layout (manifold, air bridge, and via holes) [24], [25]. ...
... Fig. 5(b) shows the R th versus W under the multiple P diss . It can be seen that with the increase of W , R th exhibits a decreasing trend and finally achieves stability, which is consistent with the heat transfer mechanism [23]. Then, the scalable thermal resistance R ths versus W sc and N sc in conjunction with the P diss is modeled as the expression ...
An accurate physical model for GaN high-electron-mobility-transistors (HEMTs) device is imperative and crucial for circuit design and technology optimization. In this paper, a scalable large-signal surface-potential (SP) model of AlGaN/GaN HEMTs is presented. The drain current model is capable of accurately modeling the self-heating effect and trapping effect. The self-heating effect is modeled by embedding temperature increment into free-carrier mobility model, and the trapping effect is modeled by introducing an indirect variable effective gate voltage $Vgseff$. Moreover, the scaling and multiharmonic characteristics of the SP model are studied for the first time. The geometry-dependent thermal resistance $Rths$ is identified by the electrothermal finite-element method simulations, which is scalable with the gate width W and power dissipations $Pdiss$ of the device. Single-tone on-wafer load-pull measurements at operating frequency 8 GHz is carried out for verification purpose. Accurate predictions of the static (dc) I-V, pulsed-gate-and-drain I-V, S-parameters up to 40 GHz and large-signal harmonic performance (the fundamental, second- and third-harmonics output power, and power-added efficiency) for the devices with different gate peripheries have been achieved by the proposed model. The results of this paper can pave the way for the full application of the physical-based model in circuits design.
... Though this FW-EM method is much more accurate, it is too complexion, and the thickness of epitaxial layer and the doping density of the device are sensitive to EM simulations, and the exact process parameters of the device needed for EM simulations tend to be confidential. As an alternative in [15], the novel distributed parasitic networks are adopted for dealing with device scaling on the basis of EM device layout simulations. Moreover, the conventional linear-scalable intrinsic model for different-in-size FET devices is inappropriate for the AlGaN/GaN HEMTs. ...
In this paper, a scalable large signal GaN HEMT model including nonlinear thermal sub-circuit is described. Only two scalable parameters are needed in the Ids scalable model by introducing a simple correction factor. The established model can predict the I–V curves at different-in-size AlGaN/GaN HEMTs devices accurately. Small signal S-parameters and large signal load pull tests with on-wafer measurement is used to further validate the proposed model. Finally, the proposed scalable model is used to design a broadband high efficiency continuous class-E power amplifier (PA). Experimental results show that this class E PA is realized from 2.5-3.5GHz with drain efficiency of 60%-70%, over 8.2dB gain and over 35.2dBm output by using a GaN HEMT with 1.25mm total gate width. The results show that the proposed model is useful for high efficiency amplifier design.
... Effects of series inductance L1 on the normalized load resistor RPout/Vcc 2 of class E amplifier with π-type network A 0.25μm gate length GaN HEMT [7,8] with 1.25 mm total gate-width is used in our design.For this transistor, the parasitic output capacitance [9,10] Cds is 0.254 pF and the parasitic output inductance Lpara is 0.15 nH. The inductance Lwire induced by bonding wire is 0.8 nH. ...
A GaN HEMTs class EF3 power amplifier (PA) with π-type network for broadband operation is presented in this paper. The π-type network is constructed by shunt capacitance, series inductance and finite dc-feed inductance, where the series inductance includes the parasitic inductance effects of transistor. As a result, the topology can make full use of the parasitic effects of transistor to raise the operation frequency. Moreover, it is found that this topology can also increase the frequency bandwidth. For demonstration purpose, a PA prototype based on the topology is fabricated. Experimental results show that the amplifier can operate from 2.9 GHz to 4.0 GHz (fractional bandwidth 31.8%) with a measured drain efficiency higher than 67%, and the output power is greater than 37.4 dBm. The proposed structure can be a good candidate for design of high efficiency and broadband class E power amplifiers.
... This method basically uses a linear scaling rule based on a reference device and thus requires more fitting procedures when scaling to large size devices. An improved scalable LSM was validated in a hybrid power amplifier with linear scalable thermal resistance in the electrothermal model in 2014 [23]. This paper shows that the scalable LSM needs four empirical parameters to fit the different size devices. ...
