The authors consider the suitability of carbon nanotubes for use in analog rf amplifiers, where linearity device is critical. They show that limit large electrostatic gate-channel capacitance, their theory predicts an Ohmically contacted, ballistic carbon-nanotube-based field-effect transistor inherently linear. While they have not achieved this experimental work, compare to experiment small capacitance and find excellent agreement at virtually all bias conditions.

The authors have designed and demonstrated a pulse-driven Josephson digital/analog converter. When used as programmable voltage standard, this device can synthesize metrologically accurate ac waveforms well stable dc voltages. We show through simulations that quantization produces nearly ideal noise spectrum when junction is driven with typical waveform produced by digital code generator. This technique has been in preliminary experiments arrays of 1000 junctions clocked at frequencies up to...

A top-gated carbon nanotube (CNT) field-effect transistor (FET) was fabricated on a quartz substrate. We used novel measurement approach and demonstrated for the first time frequency-independent performance of CNT FET frequencies as high 23GHz. This observed maximum operating frequency represents significant breakthrough in realization nanotube-based electronics applications.

Reciprocal Quantum Logic combines the speed and power-efficiency of single-flux quantum superconductor devices with design features that are similar to CMOS. We have demonstrated an 8-bit carry look-ahead adder in technology using combinational gates fanout four non-local interconnect. Measured power dissipation fully active circuit is only 510 nW at 6.2GHz. Latency 150 ps a clock rate 10GHz.

The capability of an all-niobium superconducting quantum interference device (SQUID) array to operate as electrically small antenna capable detecting radio frequency from distant sources was demonstrated. measurements were performed in three different arrays, with each consisting 2400 identical cells. intrinsic broadband characteristics the confirmed by flat response ratio output and input voltages (the S21 parameter) between 300 kHz 1 GHz. Setting its optimal operating parameters allowed...

A Josephson sigma-delta modulator suitable for use in high dynamic range conversion of MHz bandwidth signals was designed and simulated. Input signal voltages were integrated as current a superconducting inductor. single junction quantizer provided analog-to-digital (AID) at 40 GHz fed back single-flux-quantum (SFQ) voltage pulses to balance the input. JSIM calculation 13,110,000-ps interval indicated ideal first-order noise shaping 2.44-MHz voltage-source signal. Spur free 102 dB...

We report the fabrication and quasi-static testing of a two-stage, high-temperature superconducting, Single Flux Quantum shift register. The five-junction circuit was fabricated using single YBCO film, with step-edge grain boundary junctions. Storage flux, its motion in response to LOAD SHIFT signals, demonstrated at 65 K.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An analytical model has been developed to project the yield of superconductive integrated circuit chips as a function operating margins, fabrication process control, and component count. For Gaussian distributed deviations critical values from design specifications, chip was highly nonlinear (threshold) ratio margin standard deviation. Computer simulations single-flux-quantum (SFQ) logic gates with high-temperature superconductor (HTS) superconductor-normal-metal-superconductor (SNS)...

A two-loop modulator has been designed for a superconductive sigma-delta analog to digital converter. In contrast semiconductor modulators, which use high-gain amplifiers in the signal feed forward path, used gain feedback path. The of electronics precisely back single flux quantum into second integrator loop and multiple quanta first is key this circuit. simulations 40 GHz sampling rate, obtained 98 dB noise ratio on dc-60 MHz band. tolerated thermal well, obtaining SNR dc-4 band, while at...

A fabrication procedure for broad-band monolithic power GaAs integrated circuits has been demonstrated which includes formation of via holes through the 100-µm-thick substrate. selective implant <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">29</sup> Si ions into substrate is used to dope FET channel region 1.2 × 10 xmlns:xlink="http://www.w3.org/1999/xlink">17</sup> cm xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . The ohmic contacts...

Measurements have been made of the electronic thermal conductivity quench-condensed films lead-manganese and indium-manganese alloys. The results are compared with calculations based on Shiba's theory superconductors containing magnetic impurities. For Pb-Mn, value ${\ensuremath{\epsilon}}_{0}$ (the normalized position in energy gap excited state associated a single impurity) which was used earlier to explain tunneling measurements, is 0.55; this consistent our data. In-Mn,...

Interface circuits for the transfer of data between Single Flux Quantum (SPQ) have been designed, fabricated, and operated at speeds up to 3 Gigabits per second. The circuit employed an improved version SFQ/Latch converter, a Modified Variable Threshold Logic (MVTL) OR/AND gate, 3/spl times/ latching amplifier, times/-to-10/spl amplifier. amplifier stacks junctions. Resistors parallel junctions damped residual currents prevent flux trapping during reset. Tolerance critical current variations...

Superconducting digital circuits are capable of producing high dynamic range analog-to-digital converters (ADCs). We present sigma-delta architectures using large (>100) oversampling ratios to give signal-to-noise greater than 100 dB in simulation. Three distinct designs, two mechanisms for feedback, presented. All the designs use only shunted junctions, and therefore compatible with HTS SNS junctions. Simulations presented a modulator which creates feedback pulses by SQUID lobe-crossings,...

A superconductive analog-to-digital converter which uses a DC SQUID as quantizer and flip-flop counter digitizer has been designed, fabricated, tested. The circuit was fabricated using ten-level niobium process. Tests at 4.2 K demonstrated counting to the full 12-b accuracy of design, monotonic A/D conversion with linearity less than 1 LSB over more 9-b range conversion, read-on-the-fly operation overflow, gate current bus.

We have observed resistive branches in the $I\ensuremath{-}V$ characteristics of long Josephson junctions which can be simply understood terms motion individual fluxoids with reflection as antifluxoids at junction edges. The these differ qualitatively from those current singularities previously reported by Chen et al. and Fulton Dynes. Our results indicate that are not related to fluxoids.

Amplification of SFQ pulses to higher signal levels has been achieved using the general technique inductive isolation. A multiple-flux-quantum generator, which produces quantum-accurate waveforms suitable for ADC applications, and an output data link were demonstrated. Both circuits implemented critically damped, dc-powered SQUIDs stacked in series. In past, voltage achievable with this approach severely limited by parasitic capacitance ground control lines. Parasitic inhibits SQUID...

The sigma-delta architecture is the method of choice for analog-to-digital converters (ADCs) high dynamic range applications. This uses oversampling and precise feedback to generate a shaped spectral distribution quantization noise. Subsequent digital filtering suppresses out-of-band noise, yielding large signal in-band noise ratio. A unique advantage superconducting electronics availability flux quantum provide mechanically accurate at GHz rates. Josephson technology extends ADCs from MHz...

Superconductive electronics can provide low power, GHz speed spread spectrum satellite communications. The key components to construct the modem are an analog filter and a digital pseudorandom bit sequence generator, Various SFQ logic circuits required code generator. These include shift register, reset switch, XOR or XNOR. To make 4 15 four stage register with fan-out of two on each was designed. circuits, fabricated eight level Nb/AlO/sub x//Nb Josephson junction integrated circuit...

Sigma-delta analog to digital converters (ADCs) use a combination of oversampling and feedback concentrate quantization noise outside the frequency band interest. Subsequent filtering can then be used suppress yield large signal ratio. ADCs dominate high performance audio market, where is limited frequencies below 50 kHz 8 octave requires sampling rate only 25.6 MHz. Przybysz et al. have described superconductive circuit capable >40 GHz sampling, thereby extending useful bandwith tens In...

A Single Flux Quantum (SFQ) demultiplexer and a cross-bar switch for high speed data are described. Both circuits were error-free in simulation to 15 Gbps. The was two input, output (2/spl times/2) used /spl sim/400 mu/A control signals set the path. has been demonstrated at over Gbps/line using average voltage measurements. correct routing of bit stream 2.488 Gbps.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Multilevel high Tc SQUIDs, suitable for digital circuit applications, have been fabricated and tested. The devices employ a YBa2Cu3O7−δ (YBCO) ground plane, an epitaxial SrTiO3 insulator, YBCO microstrip layer. Junctions are formed by the step-edge grain boundary process, with plane contact ‘‘low’’ side of each junction, using only isotropic sputtering milling techniques. Control current is directly injected in segment SQUID loop, allowing us to measure inductance, thus infer magnetic...

A modified SNIP process was used to fabricate high-quality 0.5, 2, and 4 mu m/sup 2/ small-area Nb/AlO/sub x//Nb trilayer tunnel junctions with current densities as large 5000 A/cm/sup 2/. The average junction quality factors for the at 4.4 K were V/sub m/(2 mV)=39 mV J/sub c/=3000 m/ (2 mV)=27 c/=5000 best values of obtained 50 41 These devices designed fabricated use in a W-band mixer receiver. substrate 50- m-thick fused or crystal quartz. Special methods developed handling such thin...

Integrated circuit chips were designed and fabricated, based on a Josephson shift register that simulated operation at 25 GHz using the SPICE program. The 6.25-mm/sup 2/ chip featured twelve-gate, four-stage fabricated with Nb/AlO/sub x//Nb junctions design value of 2000 A/cm/sup critical current density. SUPERCOMPACT, general program for monolithic microwave integrated circuits, was used to model effects layout geometry uniformity phase coherence logic gate bias currents. A superconductive...

We have designed and measured single flux quantum (SFQ) circuits for data switching at 2.5 Gbps. A fully functional 2/spl times/2 node is presented. The can be used to form a larger fabric (4/spl times/4, 8/spl times/8, etc.). accepts streams either or both inputs, routing the based on address bits present in stream. This approach allows self-routing switch self-synchronous. In addition, route correctly an active input line if other idle.