JPH0390920A - Josephson regulator circuit - Google Patents

Abstract

PURPOSE:To eliminate the need for the generation of a large magnetic field by making a large current flow to a control wiring by connecting magnetically a magnetically coupled superconductive quantum interferometer to superconductive loop including two Josephson junctions. CONSTITUTION:A regulator element circuit contains a magnetically coupled superconductive quantum interferometer having a control wiring 2 connected to the power bus PB of a Josephson integrated circuit 3 at one of its both ends and grounded at the other end. Then a control signal input terminal DC is connected to the wiring 2 of the interferometer together with a sine wave current input terminal AC connected to the end of the wiring 2 which is connected to the PB of the circuit 3. In such a constitution, a superconductive current is suppressed with the small DC value and the duty is increased. Thus it is possible to obtain a Josephson regulator circuit in a simple production process.

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. This invention relates to a Josephson regulator circuit that converts the bias current into a trapezoidal waveform that is optimal for Son 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, the Technical Digest of the International Electron Devices Meeting magazine
he International Electron
Devices Meeting), 1979,
It is described on pages 489 to 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.

The Josephson regulator uses the nonlinear current-voltage characteristics of the Josephson junction to send a trapezoidal wave-shaped alternating current to the power bus of the Josephson integrated circuit connected to the terminal Out from the sinusoidal alternating current input to the terminal AC. It is a circuit.

Figure 4 shows the sinusoidal input waveform (a) applied to this Josephson regulator circuit, the trapezoidal output current waveform (when no DC current is applied to the control wiring (b), and when DC current is added (C).
)).

FIG. 4 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. 4 and 5.

First, the operation of the Josephson regulator when no current flows through the control wiring DC will be described. In this case, the output waveform is as shown in Figure 4(b), even if the input sinusoidal current increases from zero (point A), its value exceeds the critical current value (Io) of the Josephson junction. Until the voltage is exceeded, all current flows through the junction to ground, so no current flows to the output (point A-B). As the current increases further, the Josephson junction switches to a voltage state, allowing current to flow through the output (
0 point), and even if the input current increases, the operating point is in the gap region (constant voltage region) of the junction characteristics, so the output current value is shaped to a substantially constant value (point C-D). During this time, excess current flows through the Josephson junction to ground as a leakage current. The magnitude of the output current is determined by the junction gap voltage and the additional resistance of the power bus. Further, in order to keep the output current value substantially constant, it is sufficient to prevent the operating point from leaving the gap region of the junction characteristics shown in FIG. Therefore, the maximum value of the input limiting wave current may be designed so as not to exceed the maximum current value (IG) in the gap voltage region. Next, the input limited wave current is its maximum value (D
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 sub-gap region of the junction characteristic, so the Josephson junction becomes a high impedance state, and most of the input current flows to the output (point E-A). A similar operation is performed for a sinusoidal input current in the negative polarity portion because the current-voltage characteristics of the Josephson junction are symmetrical with respect to the polarity of the current and voltage.

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

This direct current removes (suppresses) the superconducting current in the Josephson junction by generating a magnetic field in the Josephson junction. The output waveform in this case is shown in Figure 4 (C
), 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 (E-D
point), 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 4(b) and 4(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 the Josephson integrated circuit operates in a region where the current value as a bias current is constant, it is desirable for the power supply to have a wide range, that is, a large duty. This is very important, especially for high-speed operation with a clock of IGHz or higher.

[Problem to be solved by the invention]

However, in the conventional Josephson regulator circuit, it is necessary to apply a magnetic field directly to the Josephson junction, and considering the area of the Josephson junction, in order to suppress the superconducting current in the Josephson junction, it is necessary to apply a magnetic field directly to the Josephson junction. The problem was that it required a large current to flow to generate a thick magnetic field. 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. For this reason, there is a problem that the element structure becomes more multi-layered and complicated.

An object of the present invention is to provide a Josephson regulator circuit that eliminates these problems.

[Means to solve the problem]

The present invention provides at least one at least one circuit connected at one end to the power bus of the Josephson integrated circuit and at the other end connected to ground.
- a regulator element circuit including a magnetically coupled superconducting quantum interferometer having a control wiring; a control signal input terminal connected to the control wiring of the magnetically coupled superconducting quantum interferometer; a sine wave current input terminal connected to one end of the Josephson integrated circuit on the side connected to the power bus, the Josephson regulator circuit comprising at least two The bottom of the cell is comprised of at least one superconducting loop including a number of Josephson junctions and one control wire 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-3QUID) used in this example.

tt2J-squID will be explained.

This is a planar magnetically coupled superconducting quantum interferometer, in which the superconducting loop la (connected to the lower wiring 1b) containing two Josephson junctions J, , J2 is connected to the ground plane (not shown). 9 control wirings 1 formed parallel to
d can be formed of a film having the same layer structure 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 wiring layer with a high layer structure to form a control wiring as in the conventional technology, so the element structure is simplified and the manufacturing process is facilitated. Furthermore, in the magnetically coupled superconducting quantum interferometer, the direct current control current required to suppress the superconducting current can be made much smaller than in the case of a single Josephson junction.

In the embodiment shown in Figure ↓, one end is connected to the Josephson integrated circuit 3.
A regulator element circuit including a magnetically coupled superconducting quantum interferometer having at least one control wire 2 connected to the power bus PB of the power bus PB and having the other end connected to ground; Consists of a control signal input terminal DC connected to the control wiring 2 of the conduction quantum interferometer, and a sine wave current input terminal AC connected to one end of the regulator element circuit on the side connected to the power bus of the Josephson integrated circuit. A Josephson regulator circuit in which a magnetically coupled superconducting quantum interferometer is connected to two Josephson junctions J, , J
l superconducting loops 1a including 2 and superconducting loop 1a
A single control wiring 1 arranged so as to be magnetically coupled to
The regulator element circuit consists of four 2J-3QUIDs connected in series and inserted between the sine wave current input terminal AC and ground.

The operation is basically the same as the conventional example.

In other words, when the control current is zero, the current up to twice the critical current value of one Josephson junction is 2J-3QUID.
is in a zero voltage state, and no current t flows on the output side. Adding a control current reduces the current value at which the Josephson junction switches to the voltage state. That is, in FIG. 4, Io
→2Io, a diagram corresponding to the operation of this embodiment can be obtained.

Superconducting current can be suppressed with a smaller DC current value than the conventional example,
Furthermore, since it is a planar type, the control wiring can be formed with the same layered film as the upper wiring forming the Josephson junction, which simplifies the manufacturing process, as described above.

In this embodiment, four two-junction superconducting quantum interferometers are connected in series, but 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 quantum interferometer instead.

〔Effect of the invention〕

As explained above, since the present invention uses a magnetically coupled superconducting quantum interferometer, it is possible to suppress the superconducting current with a smaller DC current value and increase the duty compared to the conventional example using a Josephson gate. Furthermore, by using a planar magnetically coupled superconducting quantum interferometer, it is possible to realize a Josephson regulator circuit with a simple manufacturing process.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG.
) and (b) are perspective schematic diagrams and equivalent circuit diagrams showing the outline of the magnetically coupled superconducting quantum interferometer (SQUID) portion of the Josephson regulator circuit of the present invention, and FIG. 3 is a Josephson regulator circuit according to the conventional technology. A circuit diagram showing an example of the circuit. Figure 4 shows the input current waveform and output current waveform applied to the Josephson regulator circuit. Figure 5 shows a schematic diagram of the current-voltage characteristics of the Josephson junction. It is a diagram. 1-1 to 1-4...2 junction superconducting quantum interferometer (2J-
3QUID), 2... Control wiring, 3... Josephson integrated circuit, 4... Josephson regulator, AC
...Limited wave current input terminal, DC...Control signal input terminal, Out...Output terminal, PB...Power bus.

Claims (3)

[Claims] (1) a regulator element circuit including a magnetically coupled superconducting quantum interferometer having at least one control wire connected at one end to the power bus of the Josephson integrated circuit and at the other end connected to ground; , a control signal input terminal connected to the control wiring of the magnetically coupled superconducting quantum interferometer;
and a sinusoidal 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, the Josephson regulator circuit comprising: the magnetically coupled superconducting quantum interference circuit; The total is
at least one including at least two Josephson junctions
1. A Josephson regulator circuit comprising: a superconducting loop; and a control wiring arranged to be magnetically coupled to the superconducting loop. (2) The Josephson regulator circuit according to claim 1, wherein the regulator element circuit is constituted by a circuit in which at least two magnetically coupled superconducting quantum interferometers are connected in series. (3) The Josephson regulator circuit according to claim 1 or 2, wherein the magnetically coupled superconducting quantum interferometer is a surface type.