JPS5840874A - Josephson logic circuit - Google Patents

Abstract

PURPOSE:To elevate signal amplitude voltage, and to obtain a DC power supply drive circuit operating excellently by connecting a plurality of Josephson devices, in which resistors are connected in parallel, in series. CONSTITUTION:An element 500b by the Josephson device 101b and a load resistor 102b is connected in series with a fundamental element 500a in the same constitution of the device 101a and the resistor 102a, and predetermined DC currents Ig are flowed. Control wiring 104 in the vicinity of the devices is conducted, magnetic flux generated is interlinked with the devices, and the maximum supercurrents flowing through the devices by interlinkage magnetic flux are controlled. A characteristicIis shown when both devices are under a superconducting state, a characteristic III when both are under a voltage state and a characteristic II when only one side is at superconductivity in the characteristics of the circuit, and the characteristic II can be removed through the selection of the load resistors 102. Accordingly, equivalent minimum voltage is the twice of the minimum voltage Vmin of the fundamental element single body. n arbitrary fundamental elements are connected in series and the signal amplitude of nxVmin is obtained, and the DC power supply circuit operating excellently is acquired.

Description

[Detailed Description of the Invention] The present invention provides a superconducting element! Concerning logic circuits using Josephson elements for hemorrhoids.

Logic circuits using Josephson elements are broadly classified into AC power supply drive circuits and DC power supply drive circuits.

AC power supply drive circuits require a complicated power supply system to supply power, and therefore require a complicated mounting system. The mounting system for a DC power supply drive circuit is much simpler than that for an AC power supply drive circuit, and it harmonizes well with the mounting system for conventional silicon technology. Below, a DC power supply drive circuit according to the prior art will be explained. In FIG. 1, there is a DC power source J driving circuit according to technology. One end of the -31-nonon element 101 with the load resistor 102 connected in parallel is grounded, and the other end is connected to the output terminal 107. Direct current, direct oil flowing from the d current source 103: 'M, current 1 is supplied to the Josephson element 101 and the load resistor 102. The control wiring 104 is placed near the Josephson element 101 so that the magnetic flux flowing through the terminals 105 and 106 and generated by the flow Ic of the control 14 interlinks with the Josephson element 101. Josephson element 101
The maximum superconducting current that can flow in the Josephson element 101
It is controlled by the magnetic flux that interlinks with the

Figure 2 shows the maximum superconductivity when no magnetic flux is linked to the Josephson element 101, that is, no control current flows, and the tt current is large. These are the voltage and current characteristics of the Josephson element 101 when the magnetic fluxes are interlinked, that is, when the control heart flow is flowing and the maximum superconducting current is small.

It is well known that a Josephson device can be in two superconducting states, but when the current flowing through the Josephson device in a four-voltage state is reduced, it suddenly returns to the superconducting state. . The minimum undercurrent flowing through the Josephson element for the Josephson element to remain in a voltage state is the minimum current factor 11, and the voltage corresponding to that direct current is the minimum voltage v1.
．． It is called. The minimum voltage Vm l m is roughly expressed by equation (1).

e: 4-element load 1, ,: maximum super 44' that can flow through the Josephson element
It current C1: Josephson element junction capacity As is clear from equation (1), the greater the maximum supercurrent 11 that can flow through the Josephson element, the greater the minimum voltage Vmla. Therefore, in FIG. 2, the minimum voltage Vwa I m is large, and in FIG. 3, the minimum voltage Vm l m is small. 1st
The operating point of the circuit shown in the figure is the load resistance 1 in Figures 2 and 3.
02 load linear ratio, and the voltage of Josephson element 101,
It is expressed by the intersection of the d original curves. The operating point when no control current flows is represented by point A in FIG. 2, and since the Josephson element 101 is in a superconducting state, the output terminal 107
The potential of is the ground level, that is, OV. The operating point when the control current flows is represented by point B in Figure 3,
Since the Josephson element 101 is in a voltage state, the potential of the output terminal 107 is not OV, but a finite voltage corresponding to point B appears. As is clear from the circuit operation, the voltage corresponding to 13 points is the signal amplitude voltage VA of the circuit shown in FIG. In order to achieve this kind of circuit operation, as is clear from FIG. It must be smaller than Vm la. Josephson devices can be stably manufactured when the supercurrent density is 1000 to 2000 A/ctn.
'' is the upper limit, and within this range, the signal amplitude voltage of the circuit shown in Figure 1 is only 0.5ffI or less.Therefore, the circuit shown in Figure 1 has the drawbacks of low noise and low design margin. Resistor 1 because the signal amplitude voltage is small
If the resistor 102 is made larger, the current flowing through the resistor 102 becomes smaller and the next stage circuit cannot be driven sufficiently. For example, when the superconducting current density is 2000 A/cm'', the signal amplitude voltage is 0.51 nV, and the resistance value of the resistor 102 is 10Ω.
If so, the current flowing through the resistor 102 is only a small direct current of about 50μ8. Furthermore, if the resistor 102 is designed to allow a large amount of current to flow through it, the resistance value of the resistor 102 must be made small. For example, the superconducting current density is 200OA/
cm'', the signal amplitude voltage is o, s m v, and if you try to make the current flowing through the resistor 102 1 mA, the resistance value of the resistor 102 will be 0.5 Ω.In this case, when an inductance load is driven For example, driving an inductance load of 50 P [-I causes a delay of 1 oops. In a high-speed circuit system using Josephson elements, the load resistance and impedance of the transmission line are Although it is said that 10 to 20 Ω is good, it is clear from the above explanation that the circuit shown in FIG. 1 has poor matching with the transmission line.

FIG. 4 is an example using a conventional technique for increasing the signal amplitude voltage. In the circuit shown in FIG. 4, two Josephson elements 101a and 101b are connected in series.
It has a structure that is replaced with the Josephson element 101 shown in the figure. In the circuit structure shown in FIG. 5, all Josephson elements 101a and 10T.

is in a superconducting state, the potential of the output terminal 107 is the ground potential, that is, OV, and all Josephson elements 101
When a and 101b are in a voltage state, a voltage twice as high as the signal amplitude voltage in the case of one Josephson element shown in FIG. 3 appears at the output terminal 1070. That is, in the circuit shown in FIG. 4, by connecting two Josephson elements in series, it is possible to obtain a signal amplitude voltage twice that of the circuit shown in FIG. 1. The circuit in Figure 4 shows an example in which two Josephson elements are connected in series, but if any n Josephson elements are connected in series, n of V^
It is clear that the signal amplitude voltage can be doubled. However, the circuit shown in FIG. 4 has a drawback that when no control current flows, both Josephson elements 101a and 101b and L7 do not necessarily return to the superconducting state. Below is the fifth
11J of bad luck! Explain the disadvantages of this lever. Figure 5 shows two Josephson elements 1 when no control current flows.
Voltage of 01a and 101b connected in series.

Current characteristics 1. Il, II[ and the load straight line R' of the load resistor 102 are shown. In Figure 5, 1 is a Josephson element 10
When both 1a and 1olb are in the super-conducting state,
(2) corresponds to a case in which one of the Josephson elements 101a, 101b is in a superconducting state and the other is in a voltage state, and (2) corresponds to a case in which both Josephson elements 101a, 1011) are in a voltage state. The operating points of the circuit shown in FIG. 4 when no control current flows are point A in FIG. a
, 10113 exist, one of which is in a superconducting state and the other in a voltage state. In order to operate the circuit shown in Figure 4 as a DC power supply drive circuit, the circuit shown in Figures 2 and 3 is required.
As explained in the figure, it is clear that when the control current does not flow, the normal amplitude' release pressure cannot be increased unless both edges of the Josephson cords 101a and 101b return to the superconducting state. It is inconvenient that there is an operating point such as the 0 point shown in FIG. The circuit shown in Figure 4 has δ when two Josephson elements are connected in series, but n
Similarly, when several Josephson elements are connected in series,
In other words, it is clear that there is a drawback that not all Josephsons and Hokos necessarily return to the superconducting state when no recontrol current flows.

An object of the present invention is to provide a DC power supply 1TL dynamic circuit that has a large signal amplitude voltage and operates well.

The key point of the present invention is to increase the signal amplitude voltage by connecting any number of Josephson elements in series with load resistances connected in parallel, and also to eliminate the RIS operating point as shown in Figure 4. This means that various circuits have been realized.

The present invention will be explained below using examples. ill'<
Figure 6 shows the basic element 500 of the present invention, with a load resistance of 10
It consists of a Josephson element 101 in which two Josephson elements are connected in parallel.

The control wiring 104 is placed near the Josephson element 101, and the magnetic flux generated by the control fourth current Ic flowing through the terminals 105 and 104 interlinks with the Josephson element 101.

The maximum superconducting current that can flow through the Josephson element 101 is controlled by the magnetic flux that interlinks with the Josephson element 101. The voltage and di characteristics of the basic element 500 shown in FIG. 6 are obtained by combining the voltage and current characteristics of the Josephson cable 101 and the voltage and current characteristics of the load resistor 102, and As shown in the figure. FIG. 7 shows the case where no control current flows and the maximum superconducting current that can flow through the Josephson cord 101 is large, and FIG. Superconducting current ■1 is small. Basic element 5
The minimum voltage V+s l m that remains in the voltage state of 00 is the same as that of the single Josephson element 101, and is expressed by the above equation (1). Current 1 flowing through the basic element 500 via terminals 150, 151
1 as shown in FIGS. 7 and 8, the operating point when no control current flows is point A' in FIG.
Since Josephson cord 101 is in a superconducting state, terminal 1
The voltage between 50 and 151 is Ov, and the operating point when the control current flows is point 1.1' in FIG.
Josephson cord 101 is in voltage condition at terminal 15.
The '1H pressure between 0.151 and 0.151 is not Ov, and a potential difference corresponding to the operating point B' in FIG. 6 appears. FIG. 9 shows a first embodiment of the present invention. Josephson element 101a and load resistor 102a, first basic element 5 having TTL configuration
00a, Josephson element 10lb, load resistance 10
The second basic element composed of 2b s oo b
are connected in series, one end is grounded and the other end is connected to the output terminal 107. the series-connected basic elements 500a;
500b is supplied with a direct current I from a constant current source 103. Control wiring (10) The wire 104 is placed near the Josephson elements 101a and 10 lb, and the magnetic flux generated by the control current flowing through the terminals 105 and 106 is connected to the Josephson element 10.
Interlinks with 1a and 101b. Josephson element 101a
, 101b is controlled by the interlinking magnetic flux. Basic Niremen) 500a, 5oob
Ill pressure when connected in series.

The current characteristics are f4+ by combining the voltage + #L current characteristics of the single basic elements shown in Figures 7 and 8, and are shown in Figure 1O when the control current does not flow, and as shown in Figure 11 when the control current flows. Illustrated in the figure.

In Fig. 10, I is both Josephson elements 10ta and 101b.
is in a superconducting state, and ■ is a Josephson element 101a.

One of the Josephson elements 101b is superconducting and the other is in a voltage state, and III corresponds to the case where both Josephson elements 101a, 1011) are in a voltage state. By selecting the load resistors 102a and 102b, the condition ⑅ in Fig. 11 can be completely eliminated. As shown in FIGS. 10 and 11, each of the Josephson elements 101a and 101b has a load resistor 102a.
, 102b in parallel (11), the equivalent minimum voltage of the series connection of the basic elements 500a and 500b becomes twice the minimum previous IEV, t- of the basic element Qi body. Centered flow source 103
If the DC current ■, supplied from Since both the Josephson elements 101a and 101b are in a superconducting state, the potential of the output terminal 107 is the ground potential, that is, Ov.
The operating point when control flows is point B' in FIG.
Since both terminals 101b are at one voltage point, the potential at the output terminal 107 is not OV, but a potential corresponding to point B' in FIG. 11 appears. In this case, the equivalent minimum voltage of the basic elements) 500a and 500b connected in series is twice the minimum voltage of the basic element alone, so the signal amplitude type 11' of the circuit shown in Fig. 9 is a Josephson element of 1012%. or 10.1
1) Minimum voltage that can stay at a single voltage state ■, can be increased by 2 times 1°. The circuit in Figure 9 shows an example (12) in which two basic elements) 500a and 500b are connected in series, but if any n basic elements are connected in series, the signal amplitude voltage of the circuit can be reduced to the minimum voltage V+nla. (It is clear that the minimum voltage V when the superconducting current density is 200OA/+y+"
Since 1a is 0.5 nl V, by connecting five basic elements in series, the signal amplitude voltage of the circuit shown in FIG. 9 can be increased by Z 5 In V t.

FIG. 12 shows a second embodiment of the present invention.

The circuit shown in FIG. 12 is the output terminal 10 of the circuit shown in FIG.
7 is grounded via a terminating resistor 201. When the load straight line rt" of the terminating resistor 201 is drawn in FIGS. 10 and 11 and the operating points are determined, it is point A" in FIG. 13 and B in FIG. 14.
The operating point when no control current flows is point 8 in FIG.
Since both ta and 101b are in a superconducting state, the output terminal 10
7 is 0■, and the operating point when the control '1tf current flows is point B'' in FIG. A potential corresponding to point B" in FIG. 14 appears. When the resistance value of the resistor 201 is increased, the ninth
It is clear that it is possible to realize a circuit that operates with signal amplitude voltages equivalent to the circuit shown in the figure.

FIG. 15 shows a third embodiment of the present invention.

The circuit shown in FIG. 15 is the output terminal 10 of the circuit shown in FIG.
7 is grounded via a transmission line 202 and a terminating resistor 201. Characteristic impedance Z of the transmission line 202.

It is clear that the operation of the circuit shown in FIG. 15 is the same as the operation of the circuit shown in FIG. 9 if the resistance value of the terminating resistor 201 is made equal to the resistance value of the terminating resistor 201. In the circuits shown in FIGS. 12 and 15, two basic elements 500a and 500b are connected in series, but if more basic elements are connected in series, a circuit that operates with a larger signal amplitude voltage can be created. It is clear that this can be achieved. For example, the minimum voltage 'V' when the superconducting current density is 2000 A/cm''
'+s l m is Q, 5 Ill V, so if you connect 5 basic elements in 1α column, you will get Figure 12, Figure 15.
The voltage of the circuit shown in the figure is 2.5 mV, and if the impedance of the transmission line (14) 202 and the terminating resistor 201 is 10Ω, then a +ki current of 250 μA will flow through the terminating resistor 201. I can do it. If it is this current value, it is possible to drive the next stage circuit.

Another effect of the present invention is that each Josephson element has a parallel u
The connected resistor can suppress the nonlinear resonance phenomenon that occurs between Josephson elements when basic elements are connected in series.

In the above embodiments of the present invention, the Josephson element is not specified in any way, but it is clear that the Josephson element may be a -c Josephson junction or a Josephson interferometer.

As described above, according to the present invention, it is possible to realize a circuit that has a simple structure, has a large signal amplitude voltage, and operates well when driven by a DC power supply. Therefore, by using the present invention, it is possible to realize a DC power supply drive circuit that has a wide design margin, matches well with the characteristic impedance of the transmission line, and operates stably, and has great effects.

[Brief explanation of the drawing]

FIG. 1 is an example of a DC power supply drive circuit according to the prior art, FIGS. 2 and 3 are diagrams explaining the operation of the circuit shown in FIG. 1, and FIG.
The figure shows another circuit example according to the prior art, FIG. 5 is a diagram explaining the operation of the circuit shown in FIG. 4, FIG. 6 is a configuration diagram of the basic elements of the present invention, and FIGS. 7 and 8 are the basic elements. Figures 9, 12, and 15 are diagrams for explaining the operation of the present invention, and Figures 10, 11, 13, and 14 are voltage diagrams for implementing the present invention, respectively. FIG. 3 is a diagram for explaining current characteristics. DESCRIPTION OF SYMBOLS 101... Josephson element, 102... Load resistance, 103... Constant d current source, 104... Control wiring, 201... Terminating resistance, 202... Transmission line. Agent Patent attorney Toshiyuki Usuda (15) Fig. 1 viZ Fig. 3 Art calendar / nl L -7 (16) Fig. 4 + [1e + Fig. 5

Claims (1)

[Claims] A Josephson element in which resistors are connected in parallel is used as a basic element, the basic elements are connected in series at least 21 times, a control wiring is arranged near the Josephson element, and the current flowing through the control wiring causes the Josephson element to be connected in series. Jose7non logic circuit having means for controlling the maximum superconducting current that can flow through the Son element.