JPH03152611A - Unipolar josephson regulator circuit - Google Patents

Abstract

PURPOSE:To stably increase the thermal duty and at the same time to simplify a matching operation for a planar magnetic connection type superconductive quantum interferometer by controlling a superconductive current with the small DC current value with use of said interferometer. CONSTITUTION:A planaer magnetic connection type superconductive quantum interferometer of a small current consists of a regulator element circuit 10 containing four serial 2-junction interferometers 1-1 - 1-4 and a regulator element circuit 20 containing four serial 2-junction interferometers 1-5 - 1-8 connected in parallel to a power bus PB of a Josephson IC 3. A DC current is supplied to a control wiring 2 which is magnetically connected to those interferometers 1-1 - 1-8. At the same time, the currents are supplied to the interferometers 1-1 - 1-8 from the AC and DC terminals respectively. Then a sine wave current is supplied to the IC 3 together with an optimum trapezoidal waveform bias current received via the interferometers 1-1 - 1-8. In such constitution, the superconductive current is suppressed with the small DC current value compared with use of a Josephson gate. Thus the thermal duty can be stably increased and the matching operations can be simplified among the interferometers 1-1 - 1-8.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a power supply circuit that supplies a bias current to a power bus of a Josephson integrated circuit, and more specifically, the present invention relates to a power supply circuit that supplies a bias current to a power bus of a Josephson integrated circuit. This invention relates to a Josephson regulator circuit that converts into a trapezoidal bias current suitable for integrated circuits.

[Conventional technology]

Conventionally, as such a regulator circuit for a Josephson integrated circuit, a circuit in which a circuit in which a plurality of Josephson junctions are connected in series is inserted between the power bus and the ground plane of the Josephson integrated circuit is known. . This means that
For example, Technical Digest of the International Electron Device Current Meeting Magazine
he International Electron
Devices Meeting) 1979, pages 489-492.

FIG. 3 is a circuit diagram showing an example of a Josephson regulator circuit according to this conventional technology. The operation of the conventional Josephson regulator circuit will be explained with reference to FIG. This Josephson regulator circuit is composed of four Josephson junctions connected in series and a control wiring 2 arranged so as to be magnetically coupled to each Josephson junction.

A Josephson regulator is a circuit that uses the nonlinear current-voltage characteristics of a Josephson junction to send a trapezoidal waveform alternating current to the power bus of a Josephson integrated circuit connected to a terminal Out from a sinusoidal alternating current input to a terminal AC. It is. Figure 6 shows the sinusoidal input waveform (a) applied to this Josephson regulator circuit and the trapezoidal output current waveform (
It is a figure showing the case (b) when direct current is not applied to the control wiring, and the case (c) when DC current is applied. FIG. 7 is a diagram showing a schematic diagram of current-voltage characteristics of a Josephson junction. The operating principle of this Josephson regulator circuit will be explained in more detail with reference to FIGS. 6 and 7. First control wiring D
The operation of the Josephson regulator when no current flows through C will be explained. The output waveform in this case is as shown in Figure 6(b) when the input sine wave current is zero (point A).
Even if the current increases from , as long as the value does not exceed the critical current value of the Josephson junction (0), all current flows through the junction to ground, so no current flows to the output (point A-B). When the current increases, the Josephson junction switches to a voltage state, so current flows to the output (0 point), and even if the input current increases, the operating point remains in the gap region of the junction characteristic (0 point).
(constant voltage region), the output current value is shaped to a substantially constant value (point C-D). During this time, excess current flows to ground as a leakage current through the Josephson junction. The magnitude of the output current is determined by the gap voltage of the junction and the load resistance value of the power bus, and it is necessary to prevent the output current from flowing out. Therefore, the maximum value of the input sine wave current should be designed so that it does not exceed the maximum current value (Io) in the gap voltage region.
While the output current decreases from point ) to the output current value (point D-E), the output current remains almost constant (point D-E), and when it decreases further, the operating point enters the subcap region of the junction characteristics, so the Josephson junction becomes It becomes an impedance state, and most of the input current flows to the output (point E-A).Even for a sinusoidal input current in the negative polarity part, the current-voltage characteristics of the Josephson junction change the polarity of the current and voltage. Since it is symmetrical, the same operation is performed.

Next, the operation of the Josephson regulator when direct current is passed through the control wiring will be explained.

This direct current removes the superconducting current in the Josephson junction by generating a magnetic field in the Josephson junction (
control). The output waveform in this case is shown in Figure 6 (C).
As shown in FIG. 2, while the input sinusoidal current increases from zero (point A) to the output current value, the Josephson junction is in a high impedance voltage state, and most of the input current flows to the output. When the input current reaches the output current value, the operating point in the junction characteristics becomes the gap voltage section (point E), and even if the input current increases further, the operating point remains at the gap voltage section (point E-D).
, a constant current flows through the output. The subsequent operation is the same as when no current is passed through the control line. As can be seen by comparing Figures 6(b) and 6(c), when a direct current is passed through the control line and a magnetic field is applied to the Josephson junction, the output current is more constant in the region (relative to the entire region). The ratio of this portion (called duty) increases. Since Josephson integrated circuits operate in a region where the current value is constant as the device current, it is desirable for this region to be wide, that is, to have a large duty, as a power supply, especially for IG.
This is very important in order to perform high-speed operation with a clock frequency of Hz or higher.

[Problem to be solved by the invention]

However, in the Josephson regulator circuit using conventional technology, it is necessary to apply a magnetic field directly to the Josephson junction, and considering the area of the Josephson junction, controlling the superconducting current in the Josephson junction requires a large amount of control wiring. The problem was that it was necessary to generate a large magnetic field by passing an electric current through it.

Furthermore, in the conventional Josephson regulator circuit, a bipolar trapezoidal waveform current is obtained as an output, but in a Josephson memory circuit, a unipolar trapezoidal waveform current may be required. There was a problem in that a large amount of current could not be directly supplied to the power bus.

Furthermore, in the case of integrating the circuit, after forming the Josephson junction, it is necessary to further form control wiring on top of the Josephson junction via an insulating layer. Therefore, there was a problem that the element structure became more multi-layered and complicated.The purpose of the present invention is to
The object of the present invention is to provide a Josephson regulator circuit that eliminates these problems.

[Means to solve the problem]

In the present invention, at least two regulator element circuits each including a magnetically coupled superconducting quantum interferometer having one control wire are connected in parallel between a power bus and ground of a Josephson integrated circuit, and the magnetic coupling a control signal input terminal connected to the control wiring of the type superconducting quantum interferometer; and a sine wave current input terminal connected to one end of the regulator element circuit on the side connected to the power bus of the Josephson integrated circuit. A unipolar Josephson regulator circuit comprising a DC current input terminal, wherein the magnetically coupled superconducting quantum interferometer includes at least one superconducting quantum interferometer including at least two Josephson couplings. loop and
The control wire is arranged to be magnetically coupled to the superconducting loop.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2(a)
and (b) are a schematic perspective view and an equivalent circuit diagram respectively showing a two-junction superconducting quantum interferometer (2J-8QUID) used in this example.

First, 2J-3QUID will be explained.

This is a planar magnetically coupled superconducting quantum interferometer, which has two Josephson junctions J1. A superconducting loop la (connected to the lower wiring 1b) including J2 is formed parallel to a ground plane (not shown). Control wiring 1
d can be formed of the following film in the same layer as the upper wiring layer forming the Josephson junction. This is because in a magnetically coupled superconducting quantum interferometer, the magnetic field generated by the control wiring need only be coupled to a superconducting loop containing the Josephson junction, rather than directly to the Josephson junction. Therefore, it is not necessary to newly form a higher wiring layer to form control wiring as in the conventional technology, so the element structure is simplified and the manufacturing process is facilitated. Furthermore, in a magnetically coupled superconducting quantum interferometer, the direct current control current required to suppress superconducting current can be made much smaller than in the case of a single Josephson junction. Furthermore, by connecting the regulator element circuits in parallel, it is possible to reduce the current flowing through each regulator element circuit, thereby preventing deterioration of characteristics due to heat generation of the regulator itself.

Furthermore, by applying an appropriate value of direct current from the direct current input terminal, it is possible to obtain a unipolar trapezoidal waveform current at the output of the Josephson regulator circuit.

The embodiment shown in FIG. A regulator element circuit 20 consisting of conduction quantum interferometers 1-5 to 1-8 is connected in parallel between the power bus PB of the Josephson integrated circuit and ground. The control wires of each two-junction superconducting quantum interferometer are connected to each other in series, and one end of this series-connected control wire 2 is connected to the control signal input terminal D.
The other end of C1 is connected to ground. The sine wave current input terminal AC and the DC power input terminal DC2 are unipolar in this embodiment, which are connected to one end of the regulator element circuit connected in parallel (the side to which the power bus of the Josephson integrated circuit is connected). The Josephson regulator circuit allows direct current to flow through the control wiring 2 magnetically coupled to the superconducting loops of the two-junction superconducting quantum interferometers 1-1 to 1-8.
The superconducting currents of the two-junction superconducting quantum interferometers 1-1 to 1-8 are suppressed. Furthermore, in the unipolar Josephson regulator circuit of this embodiment, two regulator element circuits 1
0.20 are connected in parallel, the current flowing through one regulator element circuit can be halved compared to when one regulator element circuit is used, which reduces the local heat generation of the regulator itself. It is possible to reduce the deterioration of characteristics due to

In addition, in addition to the sine wave AC current supplied from the sine wave input terminal AC, a DC power supply current of a value equal to the maximum value of the sine wave AC current is applied to the DC current input terminal DC2, so that the regulator can be connected to a Josephson junction. By injecting a unipolar sinusoidal alternating current as shown in FIG. 3(a) into the output terminal Out, a unipolar trapezoidal wave alternating current as shown in FIG. 3(b) can be obtained at the output terminal Out. The operating principle of this embodiment at this time will be explained in more detail with reference to FIGS. 3 and 4. FIG. 4 is a diagram showing the current-voltage characteristics of the Josephson junction of the regulator when the superconducting current is suppressed by the direct current flowing through the control wiring 2. With a DC current flowing through the control wiring 2, the input current that exceeds the regulator's unipolar sinusoidal AC current as shown in Figure 3(a) flows to ground through the Josephson junction, and the output current flows to the power bus PB. is maintained at a constant value Io (between B and CD). here,
Let vG be the gap voltage and R be the impedance of the power bus. When the input current decreases from D to E in Fig. 3(a), the Josephson junction is in the subgap region (Fig. 4D).
-E) becomes a high impedance state due to the current-voltage characteristics, and the output current of the power bus decreases as the input current decreases. Here, the output current is a constant value I between B and D.

In order to maintain the input current at a maximum value of 21. must be set below the maximum current value Io at the gap voltage ■G (21.<IO).

As described above, according to this embodiment, the manufacturing process is easy because it does not require the formation of a special wiring layer for forming control wiring, and it is possible to control the superconducting current with a small DC current value, which is also thermally efficient. Although a stable Josephson regulator can be obtained in this embodiment, four two-junction superconducting quantum interferometers are connected in series, the same effect can be obtained by using any number of two-junction superconducting quantum interferometers. Further, in this embodiment, a two-junction superconducting quantum interferometer is used, but the same effect can be obtained by using a three-junction superconducting single-son interferometer instead. Furthermore, in this embodiment, two regulator element circuits are connected in parallel, but by connecting two or more regulator element circuits in parallel, the current flowing through each regulator element circuit can be further reduced, and local Deterioration of characteristics due to generation of heat can be further reduced.

〔Effect of the invention〕

As explained above, since the present invention uses a magnetically coupled superconducting quantum interferometer, the superconducting current can be suppressed with a smaller DC current value than the conventional example using a Josephson gate, resulting in thermal stability. A unipolar Josephson regulator circuit that can have a large duty and that has a simple matching process can be realized by using a planar magnetically coupled superconducting quantum interferometer.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2(a)
and (b) is a perspective schematic diagram and an equivalent circuit diagram schematically showing the magnetically coupled superconducting quantum interferometer (SQUID) portion of the unipolar Josephson regulator circuit of the present invention, and FIG. 3(a)
and (b) is a diagram showing the input current waveform and the output current waveform of the unipolar Josephson regulator circuit according to the present invention, and FIG. 4 is a diagram showing the current-voltage characteristics of the Josephson junction used in the present invention. Figure 5 is a circuit diagram showing an example of a conventional Josephson regulator circuit, and Figures 6 (a), (b), and (c) are input current waveforms and DC power applied to the conventional Josephson regulator circuit. FIG. 7 is a diagram showing the output current waveforms in the absence and in the case of addition, and FIG. 7 is a diagram showing the current-voltage characteristics of a Josephson junction. 1-1 to 1-4...2 junction superconducting quantum interferometer (2J-
3QUID), 2... Control wiring, 3... Josephson integrated circuit, 4... Josephson regulator, 10
．． 20...Regulator element circuit, AC...Sine wave current input terminal, DCI...Control signal input terminal, DC2
...DC current input terminal, Io...output current value, 1,
... Maximum current value in the gap voltage region, Out...
Output terminal, PB power bus.

Claims (1)

[Claims] 1. At least two regulator element circuits each including a magnetically coupled superconducting quantum interferometer having one control wire are connected in parallel between the power bus and ground of the Josephson integrated circuit. , a control signal input terminal connected to the control wiring of the magnetically coupled superconducting quantum interferometer, and a sine wave connected to one end of the regulator element circuit on the side connected to the power bus of the Josephson integrated circuit. A unipolar Josephson regulator circuit comprising a current input terminal and a direct current input terminal, wherein the magnetically coupled superconducting quantum interferometer has at least one superconducting loop including at least two Josephson couplings. and a single control wiring arranged so as to be magnetically coupled to the superconducting loop. 2. The unipolar Josephson regulator circuit according to claim 1, wherein the regulator element circuit comprises a circuit in which at least two magnetically coupled superconducting quantum interferometers are connected in series. 3. The unipolar Josephson regulator circuit according to claim 1 or 2, wherein the magnetically coupled superconducting quantum interferometer is a surface type.