JPS6175574A - Superconductive switching circuit - Google Patents

Abstract

PURPOSE:To form a DCFP circuit which stably operates without erroenous operation by inserting a dampling resistor for suppressing a resonance in the DCFP circuit, thereby suppressing a resonance phenomenon. CONSTITUTION:The first and second damping resistors 201, 202 are connected in parallel with the frist and second Josephson junctions 101, 102 to suppress a resonance phenomenon to suppress the resonance phenomenon of a DCFP circuit. Thus, the operation of the DCFP circuit is stabilized, and a normal circuit operation can be performed by a small input signal. This corresponds to increase in the gain of the circuit to drive many loads by the circuit (many fanouts) to increase the functions of the DCFP circuit, thereby effectively improv ing the performance of a circuit system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electronic circuit using a superconducting element, and particularly to a switching circuit using a Josephson device.

[Background of the invention]

Switching circuits using Josephson devices are well known in the art and are typified by quantum interference circuits, direct-coupled circuits, and the like. A quantum interference circuit is a switching circuit constructed using a superconducting loop containing two or more Josephson junctions, and its details can be found in IBM Re5earc.
h and Development Vol.

24, No. 2 (1980). A direct-coupled circuit is a non-quantum interference type circuit that injects a current into a Josephson junction, and a typical example is a DCL circuit. The DCL circuit is manufactured by T E DM Tech, Diges.
It is described in detail in t (197ri). These conventional switching circuits using Josephson devices have the disadvantage that the circuit gain is as small as about 2. In addition, in order to keep a bias current flowing through the circuit, one
It consumes about 10 μW of power. Josephson devices are devices that operate at extremely low temperatures and are typically immersed in liquid helium. Compared to the heat of evaporation of liquid helium, if the LIB power dissipated per circuit is 1 to 10 μW, the amount of heat generated is large, and circuits using conventional Josephson devices are difficult to create highly integrated logic circuits and systems. ＆'lA L There are some disadvantages.

DCFP (DCF) and uxP aramctron are used as high gain and low power consumption circuits that avoid the drawbacks of these conventional circuits using Josephson devices.
) There is a circuit. Regarding the principle of DCFP circuit, Goto et al.
It is described in detail in the RIKEN Symposium ``Josephson Elec 1 Heronics'' (March 1611, 1981). A DCFP circuit is a circuit composed of a Josephson junction and an inductor. Therefore, the DCFP circuit has a drawback in that oscillation caused by a resonant circuit composed of a Josephson junction capacitance and an inductor causes a difference in circuit performance.

[Purpose of the invention]

An object of the present invention is to provide a high-gain DCFP circuit that suppresses resonance phenomena and operates stably even if a malfunction occurs.

[Summary of the invention]

In order to achieve this goal, the present invention inserts a damping resistor in the DCFP circuit to suppress resonance.

[Embodiments of the invention]

FIG. 1 is a diagram showing the principle configuration of a DCFP circuit.

DCFP @ path is a first Josephson junction], a first superconducting loop composed of 01, a first excitation inductor 103a, a load inductor 105, a second Josephson junction 102, a second excitation inductor 104a, and a load. It consists of a second superconducting loop made up of an inductor 105. Part 1. The second AIJ conductive loop shares the load inductor +05 and influences each other via the load inductor 105, so the DCFP circuit has a bistable circuit form with positive feedback. 1st. second excitation inductor], 03a, 104a are connected to power inductors 103b, l0 via transformer couplings 103, 104.
It is combined with 4b. Power supply inductor], 03 b.

1 to lance coupling]
The DCFP circuit is driven through 03, 10/I. An input signal line 108 is coupled to some or all of the load inductors 105 via a transformer coupling 106 . The operation of the DCFP circuit will be briefly explained below. The minute human power signal current ■5 is transmitted through the input signal line 108.
) When input to the CF P circuit, 1 Herance coupling 10
6, a minute current in response to the input signal current flows to the load inductor 105. In this state, power line 10
7. Two excitation inductors] When the DCFP circuit is driven through 03a and 104a, the DCFP circuit transitions to one of the bistable states according to the polarity of the minute input current 6. That is, the load current TL flowing through the load inductors 1 and 05 is determined by the input minute signal current TI. Generally, the load current TL can be made larger than the minute input current 7, and it is theoretically not difficult to make the circuit gain of the DCFP circuit 10 or more. FIG. 2 is an example of circuit simulation of the DCFP circuit shown in FIG. The circuit parameters in the example of Fig. 2 are excitation inductor], 03a, 104a are 1
．． 8pH1 load inductor 105 has a pH of 5.5.

The equivalent circuit of Josephson junctions 101 and 102 is shown in FIG.
, a model in which resistors 112 were connected in parallel was used. The maximum superconducting current of Josephson junction 110 is 50 μA, and the junction capacitance 113 is 1 pF. In FIG. 2, the first part of the DCFP circuit. The current t+rp2 flowing through the second excitation inductors 1.03a and 104a and the load current 2 of the load inductor 105 are shown. In the circuit configuration shown in FIG. 1, the junction capacitance of the first Josephson junction 101, the first excitation inductor 103a, and the load inductor 105 form a first resonant circuit.
The second Josephson junction 102, the second excitation inductor 104a, and the load inductor 105 constitute a second resonant circuit.

Therefore, when the DCFP circuit switches, an oscillation waveform due to a resonance phenomenon appears in the load current (2).

FIG. 2 shows a state in which the signal oscillates upward relative to the zero level. However, DCFP circuits require very small input signal currents. flows mixed with the load current ■. Therefore, when an oscillation waveform appears in the load current (2), it becomes an input signal and reverses the polarity of the logic circuit, causing a malfunction. In the simulation example shown in FIG. 2, the oscillation is large, so the load current T0. The polarity of is reversed, and a waveform is generated below the zero level. In this respect, a malfunction occurs. In order to prevent such malfunctions, there is a method of increasing the input signal so that the polarity does not change even if oscillation occurs, but this method does not provide a high circuit gain.

FIG. 4 shows a first embodiment of the present invention. First, to suppress the resonance phenomenon. Second damping resistor 201.202
First. It is connected in parallel to the second Josephson junction 101, 102. The resistance value of the damping resistor should be selected to be a value close to the critical damping, that is, R4 to F, where (1): the sum of the inductance values of the excitation inductor and the load inductor C: the junction capacitance of the Josephson junction. FIG. 5 shows D according to the first embodiment of the present invention.
This is an example of a simulation of a CFP circuit.

Figure 5 shows the resistance value Ra of the damping resistor 201.2'02.
This is the case when the resistance is 5Ω. However, although critical braking is performed when R2 is 3Ω, a higher resistance value is selected in order to speed up the circuit operation. As can be seen by comparing the waveform of FIG. 2, the waveform of FIG. 5 is a pulse waveform in which the oscillation phenomenon due to resonance is suppressed, and no malfunction occurs.

FIG. 6 shows another embodiment according to the present invention.

In the DCFP circuit, the load inductor 1.05 has a larger inductance value than the excitation inductors +03a, ]04a. Therefore, as shown in FIG. 6, a damping resistor 301 is connected in parallel to the load inductor, and an exciting inductor 10
It is clear that the resonance phenomenon can be suppressed by inserting the damping resistor 302 in parallel with the whole or a part of 04a.

〔Effect of the invention〕

As described above, according to the present invention, the resonance phenomenon of the DCFP circuit can be suppressed. Therefore, the operation of the DCFP circuit can be stabilized, and the circuit can operate normally even with a very small input signal.

This corresponds to increasing the gain of the circuit, which allows the circuit to drive more loads (increases the fan ouL), which is effective in enriching the functionality of the DCFP circuit and improving the performance of the circuit system. There is.

[Brief explanation of drawings]

Figure 1 is a principle diagram of a DCFP circuit, Figure 2 is a diagram showing circuit simulation results of the circuit in Figure 1, Figure 3 is an equivalent circuit diagram of a Josephson junction, and Figure 4 is a first implementation according to the present invention. An example circuit diagram, FIG. 5 is a diagram showing circuit simulation results of a DCFP circuit according to the present invention, and FIG. 6 is a circuit diagram of a second embodiment of the present invention. Explanation of symbols 1.01, 102...Josephson junction, 103a+
104a... Excitation inductor, 1.03, 104 Nidorance coupling, 105... Load inductor, 108... Input signal line, 201, . 202,301. ．． 302...damping resistance,

Claims (3)

[Claims] 1. Switching consisting of a first superconducting loop consisting of a first Josephson device, a first excitation inductor, and a load inductor, and a second superconducting loop consisting of a second Josephson device, a second excitation inductor, and the load inductor. A superconducting switching circuit characterized in that the superconducting loop includes two or more resistors. 2. A superconducting switching circuit according to claim 1, wherein the two resistors are connected in parallel to the first and second Josephson junctions, respectively. 3. In the superconducting switch circuit according to claim 1, the one resistor is connected in parallel to the load inductor, and the other resistor is connected in parallel to all or part of the first and second excitation inductors. A superconducting switching circuit characterized by: