Shawn S. H. Hsu

A 3.1–10.6 GHz Ultra-Wideband CMOS Low Noise Amplifier With Current-Reused Technique

A 3.1-10.6 GHz ultra-wideband (UWB) low noise amplifier (LNA) utilizing a current-reused technique and a simple high-pass input matching network is proposed. The implemented LNA presents a maximum power gain of 16dB, and a good input matching of 50Omega in the required band. An excellent noise figure (NF) of 3.1-6dB was obtained in the frequency range of 3.1-10.6GHz with a power dissipation of 11.9mW under a 1.8-V power supply. The proposed UWB LNA demonstrates the highest power gain and lowest NF among the published works in 0.18-mum CMOS technology

A 40-Gb/s Transimpedance Amplifier in 0.18-

A 40-Gb/s transimpedance amplifier (TIA) is realized in 0.18-mum CMOS technology. From the measured S-parameters, a transimpedance gain of 51 dBOmega and a 3-dB bandwidth up to 30.5 GHz were observed. A bandwidth enhancement technique, pi-type inductor peaking (PIP), is proposed to achieve a bandwidth enhancement ratio (BWER) of 3.31. In addition, the PIP topology used at the input stage decreases the noise current as the operation frequency increases. Under a 1.8 V supply voltage, the TIA consumes 60.1 mW with a chip area of 1.17 X 0.46 mm2. The proposed CMOS TIA presents a gain-bandwidth product per DC power figure of merit (GBP/Pde) of 180.1 GHzOmega/mW.

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Flexible integrated circuits with complex functionalities are the missing link for the active development of wearable electronic devices. Here, we report a scalable approach to fabricate self-aligned graphene microwave transistors for the implementation of flexible low-noise amplifiers and frequency mixers, two fundamental building blocks of a wireless communication receiver. A devised AlOx T-gate structure is used to achieve an appreciable increase of device transconductance and a commensurate reduction of the associated parasitic resistance, thus yielding a remarkable extrinsic cutoff frequency of 32 GHz and a maximum oscillation frequency of 20 GHz; in both cases the operation frequency is an order of magnitude higher than previously reported. The two frequencies work at 22 and 13 GHz even when subjected to a strain of 2.5%. The gigahertz microwave integrated circuits demonstrated here pave the way for applications which require high flexibility and radio frequency operations.

m CMOS Technology

This study presents a high performance K-band low noise amplifier. By utilizing transformer feedback at the input stage, an excellent noise figure (NF) of 4.3 dB is obtained at 22 GHz. With the current-reused technique between the two stages, the amplifier achieves a maximum power gain of 10.1 dB under a supply voltage of 1.8 V and a power consumption of only 7.2 mW. The proposed LNA has comparable NF and gain, while it can operate under the lowest power among the published works in 0.18 mum CMOS technology for K-band applications.

Gigahertz Flexible Graphene Transistors for Microwave Integrated Circuits

In this letter, we propose using an oxide-filled isolation structure followed by N₂/H₂ postgate annealing to reduce the leakage current in AlGaN/GaN HEMTs. An off-state drain leakage current that is smaller than 10^-9 A/mm (minimum 5.1 × 10^-10 A/mm) can be achieved, and a gate leakage current in the range of 7.8 ×10^-10 to 9.2 × 10^-11A/mm (<i>V</i> _GS from -10 to 0 V and <i>V</i> _DS = 10 V) is obtained. The substantially reduced leakage current results in an excellent on/off current ratio that is up to 1.5 × 10⁸. An improved flicker noise characteristic is also observed in the oxide-filled devices compared with that in the traditional mesa-isolated GaN HEMTs.

A Low-Power Low-Noise Amplifier for K-Band Applications

In this letter, a selective Si diffusion approach is proposed to improve both the forward and reverse characteristics of AlGaN/GaN Schottky barrier diodes on Si substrates. The Si diffusion layer forms a dual Schottky barrier anode structure, which results in a low Schottky barrier portion to reduce the onset voltage VON from 1.3 to 1.0 V (23%). In the same process step, the selectively diffused Si is adopted in the cathode to reduce the ohmic contact resistance RC and improve the breakdown voltage VBK. A low RC of 0.21 Ω·mm and enhanced VBK up to 20% (from 1250 to 1500 V) are demonstrated, which can be attributed to the alleviated electric-field peaks around the alloy spikes beneath the ohmic contact.

AlGaN/GaN HEMTs With Low Leakage Current and High On/Off Current Ratio

This letter investigates the microwave characteristics of the liquid crystal tunable capacitors for the first time. With the dielectric anisotropy properties, the liquid crystal capacitors present very different characteristics compared to the semiconductor or MEMS tunable capacitors. A quality factor of 310 with a control voltage of 5 V was achieved at 4 GHz. A tuning range of 25.3% for the control voltages from 0 to 5 V was obtained at 5 GHz. The results demonstrate the potential applications of liquid crystals as dielectric materials for capacitors with high quality factors and wide tuning ranges at high frequencies, particularly suitable for the future flexible electronics with transparent substrates.

AlGaN/GaN Schottky Barrier Diodes on Silicon Substrates With Selective Si Diffusion for Low Onset Voltage and High Reverse Blocking

InN∕AlN metal-insulator-semiconductor heterojunction field-effect transistors with a gate-modulated drain current and a clear pinch-off characteristic have been demonstrated. The devices were fabricated using high-quality InN (26nm)∕AlN (100nm) epifilms grown by plasma-assisted molecular-beam epitaxy on Si (111) substrates. The devices exhibited a current density higher than ∼530mA∕mm with a 5μm gate length. The pinch-off voltage was at ∼−7V with an associated drain leakage current less than 10μA∕mm. The observed high current density may be attributed to the high sheet carrier density due to the large spontaneous polarization difference between InN and AlN.

Microwave characteristics of liquid-crystal tunable capacitors

A compact ultra-wideband low-noise amplifier (LNA) with a 12.4-dB maximum gain, a 2.7-dB minimum noise figure (NF), and a bandwidth over 0.1-14 GHz is realized in a 0.13-μm CMOS technology. The circuit is basically an inductorless configuration using the resistive-feedback and current-reuse techniques for wideband and high-gain characteristics. It was found that a small inductor of only 0.4 nH can greatly improve the circuit performance, which enhances the bandwidth by 23%, and reduces the NF by 0.94 dB (at 10.6 GHz), while only consuming an additional area of 80 × 80 μm2. The LNA only occupies a core area of 0.031 mm , and consumes 14.4 mW from a 1.8-V supply.

High current density InN∕AlN heterojunction field-effect transistor with a SiNx gate dielectric layer

An ultra-low-power 60 GHz low-noise amplifier (LNA) with a 12.5 dB peak gain and a 5.4 dB minimum NF is demonstrated in a 90 nm CMOS technology. The LNA is composed of four cascaded common-source stages with the gate-source transformer feedback applied to the input stage for simultaneous noise and input matching. Also, the drain-source transformer feedback is used in the following stages for gain enhancement and interstage/output matching. This LNA consumes only 4.4 mW from a 1 V supply with a compact core area of 0.047 .