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Fast, Compact Josephson Star Driver

IP.com Disclosure Number: IPCOM000052447D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Gheewala, TR: AUTHOR [+3]

Abstract

In Josephson technology, Star Drivers are known for providing a plurali of outputs to other circuits. The Star Driver of Fig. 1 consists of a direct coupled (DCL) OR gate Q1 and an injection AND device Q2 the symmetric input C of which is externally provided. A resistor R isolates Q1 from Q2. The basic circuit is shown in Fig. 1 with a fan-out of 4, while the details of Q1 are shown in Fig. 3.

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Fast, Compact Josephson Star Driver

In Josephson technology, Star Drivers are known for providing a plurali of outputs to other circuits. The Star Driver of Fig. 1 consists of a direct coupled (DCL) OR gate Q1 and an injection AND device Q2 the symmetric input C of which is externally provided. A resistor R isolates Q1 from Q2. The basic circuit is shown in Fig. 1 with a fan-out of 4, while the details of Q1 are shown in Fig. 3.

Fig. 2A shows the threshold curve of Q1 while Fig. 2B shows the threshold curve of Q2 for their respective inputs A and B. Devices Q1 and Q2 are biased at a nominal value of 0.7 times their respective critical currents. Q1 consists of the DCL isolator and amplifier stages D1 and D2, which are shown in Fig. 3. Stages D1 and D2 are comprised of branches including Josephson devices J. Input A is provided to stage D1 which, when it switches, will divert its gate current I to amplifier stage D2. When D2 switches, it diverts the gate current I(g1) to the asymmetric input B of device Q2 (Fig. 1). Q2 then switches, thus diverting I(g1)+I(g2) to the outputs D, E, F, and G.

This device switches very fast and utilizes only a small amount of area on a Josephson chip. The margins of the circuit are determined by those of the first stage, the DCL isolation gate. Additionally, this circuit is compatible with current injection logic circuits.

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