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Josephson Feedback Decoder Gate

IP.com Disclosure Number: IPCOM000046103D
Original Publication Date: 1983-Jun-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Jackel, H: AUTHOR

Abstract

In self-resetting decoder gates employed in Josephson memory designs undesirable multiple switching occurs because the gate resets after the fast transfer of its gate current into the output loop into the zero- voltage state while the input control current is still present. A negative feedback scheme is proposed that eliminates the occurrence of multiple switching.

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Josephson Feedback Decoder Gate

In self-resetting decoder gates employed in Josephson memory designs undesirable multiple switching occurs because the gate resets after the fast transfer of its gate current into the output loop into the zero- voltage state while the input control current is still present. A negative feedback scheme is proposed that eliminates the occurrence of multiple switching.

Figs. 1 and 2, respectively, show the basic decoder circuit and the IG/IIN characteristic of an asymmetric 2-junction Josephson interferometer serving as a gate device. The dotted curves (A, B, C) in Fig. 2 represent the current trajectories of the dynamic operation point of the gate. The gate may reset while in the 1-mode. When the current trajectory (A) crosses the mode boundary of the 1-mode below the critical point (CP), the gate returns to its initial state in the 0-mode without a voltage transition. However, if the current trajectory crosses above CP (B), a voltage transition occurs and the gate produces an undesired second output pulse.

Fig. 3 shows the proposed decoder circuit with negative feedback. The resulting change in the current trajectory is illustrated by curve C in Fig. 2. Due to the feedback, the trajectory is substantially removed from the CP of the l- mode, thereby preventing any undesirable voltage transition. In the circuit of Fig. 3, part of the output current IOUT is fed back and inductively coupled (Lfb) to the decoder gate as control current If...