This paper presents a 3-stage differential cascode power amplifier (PA) for 109–137 GHz applications. At 120 GHz the circuit delivers 16.5 dBm saturated output power with 12.8 % power-added efficiency (PAE) without using power combining techniques. The chip was fabricated in 130 nm SiGe BiCMOS technology offering heterojunction bipolar transistors (HBT) with f T /f max of 300/500 GHz. The PA consists of three stages optimized accordingly to the design goals. The first stage operates in class A to provide high gain while the two following stages are biased in class AB and deep class AB in order to increase the efficiency. The circuit draws a maximum current of 100 mA from 3.3 V and 4 V supplies. It occupies only 0.24 mm 2 chip area excluding baluns and bondpads, which makes it attractive for future power combiners. The presented amplifier is suitable for radar applications, that require a high dynamic range.
This paper presents a highly power efficient amplifier. By stacking inverters and splitting the capacitor feedback network, the proposed amplifier achieves 6-time current reuse, thereby significantly boosting gm and lowering noise but without increasing power. A novel biasing scheme is devised to ensure robust operation under 1V supply. A prototype in 180nm CMOS has 5.5uV rms noise within 10kHz BW while consuming only 0.25uW, leading to a noise efficiency factor (NEF) of 1.07, which is the best among reported amplifiers.
Structures of the two-dimensional atomic nuclei on ZnO (0001)-Zn and (0001)-O polar surfaces were studied by first principles density functional theory. The polarity-dependent nucleation dynamics was investigated by simulating two-dimensional (2D) nuclei consisting of 1-8 ZnO monomers on both polar surfaces. According to total energy calculations, average binding energy per ZnO monomer of the surface nuclei was analyzed to investigate if the nucleation and growth will proceed reasonably in physics. We found nucleation on (0001)-Zn surface was easier than that on (0001)-O surface. By using atomistic thermodynamics analysis, we calculated the Gibbs free energy of formation of these nuclei and made a comparison between the two polar surfaces. On (0001)-Zn surface, the critical Gibbs free energy of formation is much lower than that on (0001)-O surface under the same supersaturation, which leads to a much larger ZnO growth rate and rougher morphology, in accordance with experimental results. In addition, energetic analysis of nucleation at real thermodynamic conditions was achieved by introducing the temperature-and pressure-dependent chemical potentials of ZnO precursors. (C) 2017 Elsevier B.V. All rights reserved.
