5,047 research outputs found
High Current Matching over Full-Swing and Low-Glitch Charge Pump Circuit for PLLs
A high current matching over full-swing and low-glitch charge pump (CP) circuit is proposed. The current of the CP is split into two identical branches having one-half the original current. The two branches are connected in source-coupled structure, and a two-stage amplifier is used to regulate the common-source voltage for the minimum current mismatch. The proposed CP is designed in TSMC 0.18µm CMOS technology with a power supply of 1.8 V. SpectreRF based simulation results show the mismatch between the current source and the current sink is less than 0.1% while the current is 40 µA and output swing is 1.32 V ranging from 0.2 V to 1.52 V. Moreover, the transient output current presents nearly no glitches. The simulation results verify the usage of the CP in PLLs with the maximum tuning range from the voltage-controlled oscillator, as well as the low power supply applications
Thermal entanglement and teleportation in a two-qubit Heisenberg chain with Dzyaloshinski-Moriya anisotropic antisymmetric interaction
Thermal entanglement of a two-qubit Heisenberg chain in presence of the
Dzyaloshinski-Moriya (DM) anisotropic antisymmetric interaction and
entanglement teleportation when using two independent Heisenberg chains as
quantum channel are investigated. It is found that the DM interaction can
excite the entanglement and teleportation fidelity. The output entanglement
increases linearly with increasing value of input one, its dependences on the
temperature, DM interaction and spin coupling constant are given in detail.
Entanglement teleportation will be better realized via antiferromagnetic spin
chain when the DM interaction is turned off and the temperature is low.
However, the introduction of DM interaction can cause the ferromagnetic spin
chain to be a better quantum channel for teleportation. A minimal entanglement
of the thermal state in the model is needed to realize the entanglement
teleportation regardless of antiferromagnetic or ferromagnetic spin chains.Comment: 1 tex;5eps. accepted by Physical Review
Mechanism for current saturation and energy dissipation in graphene transistors
From a combination of careful and detailed theoretical and experimental
studies, we demonstrate that the Boltzmann theory including all scattering
mechanisms gives an excellent account, with no adjustable parameters, of high
electric field transport in single as well as double-oxide graphene
transistors. We further show unambiguously that scattering from the substrate
and superstrate surface optical (SO) phonons governs the high field transport
and heat dissipation over a wide range of experimentally relevant parameters.
Models that neglect SO phonons altogether or treat them in a simple
phenomenological manner are inadequate. We outline possible strategies for
achieving higher current and complete saturation in graphene devices.Comment: revtex, 5 pages, 3 figures, to appear in Phys. Rev. Lett
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