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Regulated Power Supply With Adjustable Dwell for Josephson Logic Circuits

IP.com Disclosure Number: IPCOM000053018D
Original Publication Date: 1981-Aug-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 3 page(s) / 56K

IBM

Related People

Gheewala, TR: AUTHOR

Abstract

In circuits using Josephson tunneling devices, a phenomenon known as punch-through can occur when the AC power supply changes its polarity. When this occurs, the Josephson device will remain in its non-zero voltage state rather than reset to its superconducting state as the gate current through the device is reduced when the power supply waveform changes from one polarity to the opposite polarity. The probability for this depends upon the rate of change of the gate current. To reduce this probability, a dwell-time in the power supply waveform near its zero-crossing is desired. This dwell-time is produced by adding together two regulated AC waveforms which are separated by a delay. This is achieved through the use of Josephson regulator circuits comprising series Josephson devices.

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Regulated Power Supply With Adjustable Dwell for Josephson Logic Circuits

In circuits using Josephson tunneling devices, a phenomenon known as punch-through can occur when the AC power supply changes its polarity. When this occurs, the Josephson device will remain in its non-zero voltage state rather than reset to its superconducting state as the gate current through the device is reduced when the power supply waveform changes from one polarity to the opposite polarity. The probability for this depends upon the rate of change of the gate current. To reduce this probability, a dwell-time in the power supply waveform near its zero-crossing is desired. This dwell-time is produced by adding together two regulated AC waveforms which are separated by a delay. This is achieved through the use of Josephson regulator circuits comprising series Josephson devices.

Fig. 1 shows an AC power waveform 10 which provides a gate current I(g) to a Josephson device. The punch-through probability decays exponentially with the time interval T(x), which is the interval the gate current spends going from +I(min) to -I(min). In order to lower the punch through probability to an acceptable level, T(x) has a value given by the circuit lithography and the total inactive time of the power supply T(t).

A scheme to generate a power supply waveform with adequate T(x) but not too large a T(t) is illustrated in Fig. 2. Waveforms A and B are trapezoidal AC waveforms which are separated from one an...