No abstract

No abstract

A 2.67 fJ/c.-s. 27.8 kS/s 0.35 V 10-bit successive approximation register analogue-to-digital converter in 65 nm complementary metal oxide semiconductor Abstract: A design of a 10-bit 27.8 kS/s 0.35 V ultra-low power successive approximation register (SAR) analogue-to-digital converter (ADC) is presented. Nano-watt range power consumption is achieved thanks to the proposed segmented-capacitor array structure and ultra-low voltage design. To facilitate ultra-low voltage operation, a bulk-driven based fully dynamic comparator is proposed. A novel latched dynamic logic cell is introduced to eliminate decision error caused by leakage current. Boosting technique is introduced in digital-to-analogue converter (DAC) driving switch to relieve non-linearity. A new double-boosted sample switch is employed to reduce leakage current and improve sampling linearity. The ADC was fabricated in 65 nm complementary metal oxide semiconductor. Drawing 25.2 nW from a single 350 mV supply, the ADC achieves 52.14 dB signal-to-noise distortion ratio and 8.4-bit effective number of bits resulting in a figure-of-merit of 2.67 fJ/ conversion-step.

Rectangularwaveguides with two conventional and two superconducting walls RAJ YALAMANCHILIt, ZHENG AN QIUt and YEN-CHU WANGtThe propagation properties of TEm" modes and their dispersion relations in rectangular waveguides with two conventional and two superconducting walls, derived by using the Meissner boundary conditions on the superconducting walls, are presented. In addition to recovering some previously known results, some novel results have been obtained: the cut-off wavelength of the dominant TE t°m ode is greater than that of the conventional TE_o mode, and the tangential electric field and normal magnetic field for the dominant mode TE 1°exist on the superconducting surfaces. Expressions for electromagnetic components, surface currents, attenuation coefficient, maximum transmitted power, dispersion and wave impedance are also presented.

The dynamics of fluxons in the vortex flow transistor (VFT) has been much studied. The fluxon transit time determines the fundamental speed limit of operation. Since fluxons can travel at the velocity of electromagnetic waves in the junction, the VFT has the potential for operating in high frequency systems ('" 100 GHz). However, owing to the low input and output impedance of the VFT, use of the device in a conventional circuit would be quite limited. A distributed amplifier configuration consisting of many VFTs has been proposed to remedy the problems of low impedance levels. However, the realization of such an amplifier circuit at microwave or millimetre wave frequencies depends on obtaining a circuit model. In this paper, microwave superconducting VFT distributed amplifiers using the balanced control technique is reviewed. This kind of amplifier has the advantage that the capacitive feedthrough effect is decreased to a negligible extent. This is the major limiting factor for high frequency applications. The self-field effect which makes the current step inclined is reduced by injecting bias current only around the region of one end of the junction thus obtaining steeper 1-V characteristics. With the asymmetric geometry, the slope of the current step is about one hundred times steeper than those obtained with the conventional overlap geometry. Owing to the diamagnetic behaviour of the Josephson junction, a little of the magnetic field induced by the current in the control line is allowed to penetrate the junction. Thus, the transresistance rm of a VFT is very small. Some methods for maximizing r., and minimizing the output impedance r., also appear in this review. The feasibility of fabricating VFT distributed amplifiers using low-1;, superconducting material has been demonstrated. The power gain of the amplifier can be as high as 15dB with a flat frequency response. NotationI length of the junction c electromagnetic wave velocity in the junction v velocity of fluxon <1>0 flux quantum 4> phase difference between the two electrodes <1> magnetic flux J 0 maximum Josephson current (critical current) density 1 0 maximum Josephson current (critical current) I b bias current J b bias current density I m maximum microwave signal current I total tunnelling current Ie current in control line