Experimentally verified design guidelines for minimizing the gray zone width of Josephson comparators

Ebert, B.; Mielke, O.; Kunert, J.; Stolz, R.; Ortlepp, Thomas

doi:10.1088/0953-2048/23/5/055005

Cited by 20 publications

(8 citation statements)

References 10 publications

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“…The device under test shows an effective grey zone of GZ ≈ 30 0 . Taking into account the inductance of the input coil L ≈ 7 nH (calculated with FastHenry [13]), the grey zone GZ I results in ≈8.9 µA which corresponds to the expected value [14] and proves the validity of the behavioural model.…”

Section: Influence Of Grey Zone On Harmonic Distortionsupporting

confidence: 56%

Optimization of a digital SQUID magnetometer in terms of noise and distortion

Haverkamp

Wetzstein

Kunert

et al. 2012

Supercond. Sci. Technol.

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The digital SQUID magnetometer takes advantage of flux quantization in a superconducting loop in order to measure magnetic fields. The core element of the digital SQUID is a Josephson comparator with a superconducting antenna loop attached to one of its junctions. Evaluation of the circuit from the system's point of view requires an analysis in the frequency domain. In order to obtain a high-resolution fast Fourier transform, large datasets are necessary which are difficult to generate with transient simulation tools. In this work we derive a behavioural model for the digital SQUID in order to overcome restrictions imposed by transient simulation. By means of this model the influence of the comparator grey zone and the input loop inductance on the system performance was analysed. In order to assess the system, evaluation criteria based on the power spectral density were applied, which are commonly used for characterization of semiconductor analogue to digital converters. As a result of this study, design guidelines for an optimum antenna inductance depending on the comparator grey zone are derived, allowing us to achieve an optimum system performance in terms of noise and distortion.

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Section: Influence Of Grey Zone On Harmonic Distortionsupporting

confidence: 56%

Optimization of a digital SQUID magnetometer in terms of noise and distortion

Haverkamp

Wetzstein

Kunert

et al. 2012

Supercond. Sci. Technol.

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“…These transition curves have been measured for a sequence of different bias current values to study the bias current dependency in detail. The gray zone of several comparator topologies was investigated in [8] whereat a minimum gray zone of 3.2 μA was obtained in experiments. The applied circuit model in this work did not provide a reasonably good agreement between circuit simulations and experiments.…”

Section: Circuit Under Investigationmentioning

confidence: 99%

“…The experiment is based on counting the output pulses with respect to the number of pulses provided to the clock input. We implemented a testbench as described in [8]. We analyzed the gray zone as a function of the bias current.…”

Section: Model Verificationmentioning

confidence: 99%

Experimental Analysis of the Bias Dependent Sensitivity of a Josephson Comparator

Haddad

Engert

Brandel

et al. 2015

IEEE Trans. Appl. Supercond.

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The Josephson comparator is one of the building blocks of superconductor electronics. It is used as a decision element in all analog and digital circuits. For fast high-bandwidth analog-to-digital converters as well as for digital circuits with reduced switching energy its high sensitivity is most important. Thermal noise limits its decision uncertainty. In this work we analyze the influence of the bias current on the gray zone of a Josephson comparator. Circuit simulations are compared against experimental data. The experimental analysis shows a characteristic dependence of the gray zone on the bias current. We can identify a clear minimum value. This point is related to a certain clock frequency. At low frequencies the simulated relationship between the gray zone and the bias current is in very good agreement with experimental results. The comparison confirmed the circuit model and enables to adjust the design to certain applications to realize the best trade-off between clock frequency and grey zone. The article describes the experimental validation procedure and a derived normalized dependency in detail.

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“…Therefore, the pseudo sigmoid function generator can be implemented using the characteristic of the SFQ comparator. The gain of the sigmoid function and the offset of the input can be adjusted by optimizing the circuit parameters of the SFQ comparator [14].…”

Section: Design Of Pseudo Sigmoid Function Generatormentioning

confidence: 99%

Pseudo Sigmoid Function Generator for a Superconductive Neural Network

Yamanashi

Umeda

Yoshikawa

2013

IEEE Trans. Appl. Supercond.

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A superconductive perceptron, an artificial neural network, has been investigated using single flux quantum (SFQ) stochastic logic. A superconductive pseudo sigmoid function generator that corresponds to an artificial neuron device for the perceptron has been proposed and implemented using an SFQ current comparator and a frequency-to-current converter, which generates current that is proportional to the average input SFQ frequency. A frequency-to-current converter has been implemented using a dc-SQUID voltage driver coupled with a Josephson transmission line. We implemented and tested the pseudo sigmoid function generator using the SRL 2.5 kA/cm 2 Nb process. The measured input-output characteristic agreed with the ideal sigmoid function with an average error of 0.063%.

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Experimentally verified design guidelines for minimizing the gray zone width of Josephson comparators

Cited by 20 publications

References 10 publications

Optimization of a digital SQUID magnetometer in terms of noise and distortion

Optimization of a digital SQUID magnetometer in terms of noise and distortion

Experimental Analysis of the Bias Dependent Sensitivity of a Josephson Comparator

Pseudo Sigmoid Function Generator for a Superconductive Neural Network

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