JPS60260225A - Josephson or circuit - Google Patents

Abstract

PURPOSE:To obtain a Josephson OR circuit possible for obtaining a large current gain by using an injection type interference element and a magnetic field coupling type interference element to constitute an injection type superconduction quantum interference element. CONSTITUTION:When a bias current is inputted to an inductance L5 from a terminal 6, a current corresponding to the bias current is induced to the L4 coupled magnetically with the L5, and the current flows to the injection type supervonduction quantum interference element 1 comprising Josephson JS junctions 2, 3 and the L4. Moreover, the bias current inputted from the terminal 6 is inputted to the interference element 1 through the L5. The current flowing to the interference element 1 is increased by the injection of the bias current and even if an input signal inputted via a JS element 7 is small, a sufficient load current to drive a load resistor 10 is supplied from the output of the interference element 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to an OR circuit, and more particularly to a Josephson OR circuit that uses Josephson elements and has a large current gain.

(2) Background of the invention A superconducting quantum interference device using multiple Josephson junctions (
There are two types of interference elements (hereinafter referred to as interference elements): injection type interference elements and magnetic field coupling type interference elements, depending on how a bias current is applied. Injection type interference elements input bias current directly into the Josephson junction.

A magnetic field coupling type interference element is one in which a control line is provided outside the interference element to magnetically control the interference element.

(3) Conventional technology and problems In particular, using an injection type interference element, the logical sum (hereinafter referred to as "disjunction") is used.

There are many examples of configuring circuits (denoted as OR).1For example, an injection type quantum interference device is constructed using two Josephson junctions in parallel as shown in Figure 1+a+, and a bias current is injected into the inductance of the junction. Then, when input signals are input to the two Josephson junctions, a load current is supplied to a load resistor (not shown) connected in parallel to the interference element. That is, when both the bias current and the input signal are input to the OR circuit constituted by two Josephson junctions, the bias current is taken out as the output of the OR circuit.

Figure 1 (bl shows the dark value characteristics of the bias current and the input current to enable a sufficient current to be supplied to the load resistance of an OR circuit using a conventional injection interference element of 1tm(al). This is a diagram. In the figure, the horizontal axis shows the input current, and the vertical axis shows the bias current. There are multiple dark value characteristic curves depending on the magnitude of the bias current and the input current, and the input current However, there may be two bias currents that can supply the output current, and one curve is not a single value function but a multivalue function.

Figure 1 (C1
For example, the slope of curve I is the ratio of input current 1 to bias current 3, and the slope is small, so in conventional OR circuit using injection type interference element, the slope is small, so in conventional OR circuit, bias current is low. In this case, it is necessary to increase the input current in order to obtain a sufficient output current, and therefore the gain is small.

(4) Purpose of the Invention In view of the above-mentioned conventional drawbacks, the present invention makes it possible to obtain large current and gain by constructing an interference element using an injection type interference element and a magnetic field coupling type interference element. It is an object of the present invention to provide a Josephson OR circuit that has the following characteristics.

(5) Structure of the Invention According to the present invention, the above objects include: an injection type superconducting quantum interference device having an input/output separation means; a magnetic field coupling means for magnetically coupling a bias current to the superconducting quantum interference device; injection means for injecting the bias current into the conduction quantum interference element, the bias current is caused to flow through the magnetic field coupling means, and then the bias current is injected into the superconducting quantum interference element via the injection means. This is achieved by providing a Josephson OR circuit characterized by .

(6) Examples of the invention Hereinafter, two embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is an equivalent circuit diagram of the Josephson OR circuit of the present invention.

In the figure, interference element 1 is a Josephson junction 2.3
．． It consists of a superconducting closed loop with an inductance of 4. The inductance 5 is magnetically coupled to the inductance 4, one end of the inductance 5 is connected to a terminal 6 into which a bias current is input, and the other end is connected to the interference element l. That is, the feature is that the bias current is magnetically coupled to the interference element (1) before being injected into the interference element (2). The Josephson junction 7 and the resistor 8 are elements for separating the input signal input from the terminal 9 and the output of the interference element 1,
Further, the load resistor 10 is a resistor for taking out the output of the interference element 1.

The operation of the Josephson OR circuit configured as above will be explained below.

When a bias current is input to the inductance 5 from the terminal 6, a current corresponding to the bias current is induced in the inductance 4 magnetically coupled to the inductance 5, and the Josephson junctions 2, 3, . A current flows through the interference element 1 of inductance 4 . Further, the bias current inputted from the terminal 6 is inputted to the interference element 1 through the inductance 5. By injecting this bias current, the current flowing through the interference element 1 described above increases, and even if the input signal input from the terminal 9 through the Josephson element 7 is small, the load resistor 10 can be driven from the output of the interference element 1. A sufficient load current can be supplied.

Therefore, if the same bias current as in the conventional case is input from the terminal 6, the signal input to the terminal 9 can be small. The dark value characteristics at this time are shown in FIG. In the same figure, 13.
14 shows a dark value characteristic curve. In the figure, the value of inductance 4 is L, and the critical current of Josephson junction 2.3 is In
When the coupling coefficient of inductance 4.5 is K and the magnetic flux density is Φ0, +:, Ljo/Φ0 is 0.65.
This is the dark value characteristic with K set to 0.4, and if the bias current and input current are controlled so as to utilize the very large curve 14, even if the bias current and input current are small, the interference element 1, it is possible to obtain an output current sufficient to drive a load.

FIG. 4 is an equivalent circuit diagram showing another embodiment of the Josephson OR circuit of the present invention, which is a circuit that can control the bias current and input current to utilize the dark value characteristic 14 with a large slope in FIG. be. In this figure, the same parts as those in FIG. 2 are given the same numbers, and the explanation of the structure will be omitted.

The difference from FIG. 2 is that a Josephson element 12 and a resistor 8 are added. That is, one end of the inductance 5 is connected to the terminal 6 as in FIG. 2, but the other end is input to the interference element 1 via the resistor 11. Further, a Josephson junction 12 for absorbing the initial current of the bias current flowing through the inductance 5 is provided between the connection point between the inductance 5 and the resistor 11 and the ground.

The operation of the Josephson OR circuit configured as above will be explained below.

The bias current input from terminal 6 is input to inductance 5, and due to the magnetic coupling between inductance 4 and inductance 5, a Josephson junction 2°3 and inductance 4 are formed.
Current flows through the circuit. The initial current flowing through the inductance 5 flows into the Josephson junction 12 because a superconducting current flows through the Josephson junction 12, does not enter the interference element 1, and flows through the Josephson junction 12 to the atmosphere-b''r ground. When the bias current increases and exceeds the critical current, the Josephson junction 12 switches and becomes the Josephson junction 12.
The resistance value of is defined as the high resistance value. Therefore, the bias current flows to the output via the resistor 11 having a low resistance value. Further, the interference element 1 is connected to the terminal 9 via the resistor 7, as in the above-mentioned embodiment.
An output current is caused to flow through the load resistor 10 in response to an input signal input to the load resistor 10.

FIG. 5 is a diagram in which the movement of the operating point in the circuit of this embodiment is mapped onto the dark value characteristic of FIG.

The initial bias current input from the terminal 6 flows into the Josephson junction 12 and does not input into the interference element 1, so only the induced current due to the magnetic coupling between the inductances 4 and 5 occurs.
As shown in the figure, the operating point moves to the 0 point delayed by the angle θ. When the bias current is further increased, the Josephson elements 2 and 3 have a high resistance, so that the bias current is passed through the resistor 11 to the output side. At this time, the operating point moves to point A, and the bias current becomes higher than the curve 13 where the input current is zero.

In this way, by moving the operating point of the bias current to o-c-A, the dark value curve 13, which causes mis-switching of the interference element 1, can be bypassed without crossing it, so the operating point can be moved to point A. Therefore, there is no possibility of malfunction, and the interference element 1 can be operated using the dark value curve 14 with a large slope required by the input current, and the gain can be increased.

(7) Effects of the Invention As explained in detail above, according to the present invention, a large current gain can be obtained with a simple configuration in which the bias current input to the injection interference element is magnetically coupled with the inductance of the interference element9. The use of the OR circuit of the present invention has the effect of expanding the margin in circuit design.

[Brief explanation of drawings]

FIG. 1 is a dark value characteristic diagram of a conventional interference element, FIG. 2 is an equivalent circuit diagram of a Josephson OR circuit according to the present invention, and FIG. 3 is a dark value characteristic diagram of a Josephson OR circuit according to the present invention. FIG. 4 is an equivalent circuit diagram of another Josephson OR circuit according to the present invention, and FIG. 5 is a configuration diagram illustrating the operation of the interference element. 1----Superconducting quantum interference device, 2.3,7゜12-
'---Josephson junction, 4. 5------
Inductance, 13.14 ---- Dark value characteristic curve Figure 1 (Q) Figure 1 (C) Figure 2 ± Figure 3', 4 Figure 5

Claims (2)

[Claims] (1) An injection type superconducting quantum interference device having an input/output separation means, a magnetic field coupling means for magnetically coupling a bias current to the superconducting quantum interference device, and an injection for injecting the bias current into the superconducting quantum interference device. A Josephson OR circuit comprising: means for causing the bias current to flow through the magnetic field coupling means, and then injecting the bias current into the superconducting quantum interference device via the injection means.ゝ・− (2) The Josephson OR circuit according to claim 1, wherein the injection means uses a Josephson junction and a resistor to inject a part of the bias current into the superconducting quantum interference device. .