JPS62211712A - Josephson regulator - Google Patents

Abstract

PURPOSE:To stably operate a Josephson digital circuit by taking out the current in a superconductive quantum interferometer (SQUID) with a superconductive load inductor and supplying it to a Josephson gate through a dropping resistor. CONSTITUTION:The circuit consists of the loop of an input inductor 9 in which input current Ip flows, a SQUID loop 7, and a load loop 8. The SQUID loop 7 is constituted of the first superconductive inductor 10 connected magnetically with an input inductor 9, a Josephson junction 6 (shunt resistance Ro 14) and the second supercondcutive inductor 11. The load loop 8 is made up of a superconductive load inductor 12 connected magnetically with the second superconductive inductor 11 of the loop 7 and plural series circuits of one Josephson gate 3 and one dropping resistance 2 connected in parallel and inserted between two terminals of a superconductive load inductor 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a digital circuit regulator, and more particularly to a bias current regulator for a digital circuit.

[Conventional technology]

In digital circuits that require a bias supply current with a trapezoidal waveform, Yabu Yabo ≠ ad heat conventionally, Ni Ivy Φ Conference Proceedings X (AI
P Conference Proceedings)
, 44 volumes, 1978, I! As described on page 470, a digital Sefson regiator was used that utilized the nonlinear 1-V characteristic of quasiparticle tunneling in a Sefson tunnel junction. This conventional non-regiator is constructed by inserting Qm Josephson junctions connected in series between the power supply bus and the ground terminal as shown in Figure 3.

In Fig. 3, 1 is a regierator junction consisting of m Josephson junctions connected in series, 2 is a dropping resistor with a resistance value R, 3 is a Josephson digital gate, 4 is a load resistance of the Josephson digital gate 3, and 5 is a 1 This is the source bus. w, as you can see from Figure 3, the dropping resistance 2
, Josephson digital gate 3, and load resistor 4 are each connected to n@power supply lot 5. The operation of this regulator will be explained with reference to FIG. 4 (Ta, et al.). Figure 4 (I-V% relationship diagram of alH regierator junction,
The horizontal axis is the voltage ■, and the vertical axis is the N flow I. IO is the critical current of regulator junction 1, Iac is the maximum input current, and Vg is the gap voltage. Figure 4 is a characteristic diagram showing temporal changes in the input current and output current to the regulator junction 1, where the vertical axis is the current and the horizontal axis is the time t. Figure 4 (
The sinusoidal input current shown by the dashed line in bl is a voltage change according to Fig. 4 (current step due to quasiparticle tunneling during the I-V% characteristic of one regulator junction (wL4 diagram (between d and e in al)). The output current shown in ) in Fig. 4 flows on the W source bus 5. The flat part of this output current (between υ and ded in Fig. 4) This is the operation period for supplying bias current to the digital circuit. -The ratio of operating periods in a cycle is called duty, and the larger the duty, the better the efficiency of the digital circuit.

Some of the problems with conventional Josephson regulators are discussed below.

(1) The fluctuation of the 'N current value during operation is dependent on the sharp current rise at the gap voltage due to quasiparticle tunneling in the regulator junction. In other words, WL4 diagram (a
) The larger the slope between de and the lower the variation in the output ti value. The fluctuation of output current value ΔI and the average value of output current I
The ratio of out, ΔI/Iout, is around 7% in commonly used P, b-based junctions. Such a large variation in bias current value greatly limits the operating margin of each Josephson digital gate.

2) Sine waveform 1 input to Josephson regulator
Approximately half of the energy is consumed in the generator, producing heat. The higher the duty, the more significant this heating effect becomes. This heat causes deterioration of the I-V characteristics of the regulator junction, further increasing the aforementioned bias current value variation Δl. This exothermic effect is produced by IDM Technical Digests (I
EDM Technical Digests), 2nd
It is reported in Vol. 4, No. 2, 1979, page 489, etc., that the current value fluctuation ΔI/Iout of a Josephson regulator with 9D 0% made with Fb-based junctions is reported.
is as high as 12%, which is very likely to cause malfunctions of Josephson digital gates.

(3) Average value m of output current of Josephson regulator
v g is I. It is utsa-1-. If the bias ta required for each Josephson digital gate is 1g, then 1
The current to be output to the source bus 5 is nIg=nαIc. In this case, Ic is the critical current value of each Josephson digital gate, and α is a constant determined at the time of circuit design, usually 0.5.
<αkl. Therefore, the relational expression t = 1 is satisfied α
R1c must be added. α9m is constant, vg is a physical constant, but the dropping resistance R and the gate critical '[current Ic] are variables that vary independently from the design value due to process conditions, etc., so the above 'H'FCT The relationship "c=" is not necessarily satisfied as designed. If R, Ic, etc. deviate from the designed values, the designed optimum bias condition of Ig=+αIc will not be maintained, leading to margin deterioration or malfunction.

[Problem that the invention seeks to solve]

The conventional Josephson regulator described above mainly has a simple configuration in which multiple dielectric junctions are connected in series, so the stability of the output current, temperature changes, and manufacturing variations are large, resulting in poor operation. The drawback is that the margin is small and malfunctions are likely to occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a low-cost non-regiator with improved constant current characteristics.

[Friendly means of solving problems]

The Josephson regulator of the present invention uses a Josephson junction. 1st. a superconducting quantum interferometer in which a second superconducting inductor is connected in a ring shape; an input inductor magnetically coupled to the first superconducting inductor; It has a conductive load inductor, and a unit circuit including a series circuit of one Josephson gate and one dropping resistor, which is inserted in parallel connection between both terminals of the superconducting load inductor. It is something.

[Effect]

In the present invention, a nonlinear circulating flow flowing through a superconducting quantum interferometer (SQUID) is taken out by a superconducting load inductor and supplied to a Josephson gate via a dropping resistor.

〔Example〕

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

FIG. 1 is a circuit diagram of an embodiment of the present invention.

This example uses a Josephson junction 6 (shunt resistor RO
), 1st. A superconducting quantum interferometer 7 in which a second superconducting inductor 10°11% (inductance L1 m '' 2 )% is connected in a ring shape, and an input inductor 9 (inductance L
p ) and a superconducting load inductor ≠ 412 (inductance L
t) and a plurality of unit circuits connected in parallel and inserted between both terminals of the superconducting load inductor 12 and including a series circuit of one Josephson gate 3 and one dropping resistor 2 (resistance R). It is something that you have.

Next, before explaining the operation of this embodiment, a single junction 8QU
The ID circulation@current will be explained.

Wcz diagram (a) is a characteristic diagram showing the relationship between external magnetic flux and circulating current in a single-junction 5QUID during quasi-static operation.

In FIG. 2(a), the horizontal axis is the external magnetic flux ΦeX applied to the external 5QUID; the vertical axis is the critical current of the Josephson junction that circulates through the 5QUID circuit, and the inductance of the LH8QUID loop. Figure 2 (ωThe solid line indicates the stable point of the circulating current, and the arrow indicates that the external magnetic flux Φex is Φex''
This is the direction of change in the stable point when increasing by o. As can be seen in FIG. 2(a), as Φex changes, Is reaches the maximum value IOK and then rapidly changes by Δ1, drawing a waveform like a tooth saw blade. Every time the current changes by Δ1,
The quantum state of 5QUID is = 0.1.2.3...
・Changes. In FIG. 2(a), the modulation blindness ΔIi of Is can be seen (β in ml is about 1-2).

In Fig. 2), 5QUID with β = 100 and Φ of sine waveform
The figure shows the temporal change in Is when ex is applied.

Figure 2 (in BL, the horizontal axis is time t, the vertical axis is IS, the dotted line is Is when the Josephson junction is removed from the 8QTJID loop, and the solid line is the actual process 3. During the operation period when Φ) is shown in the conventional current waveform (FIG. 4)) and the peak in FIG. 2, there are countless sawtooth-shaped quantum states as shown in FIG. The time interval Δt between adjacent quantum states is expressed as follows as a function ω of the duty D, the periodicity of the clock, and β.

However, the time for the quantum state of 5QUID to transition from K to +1 is physically limited, and IBM
IBM Journal of Research and Development
rchand Development), IE
As stated in Vol. 24, p. 143, 1980, it is simply the shunt resistance of the superjunction, and in the microbridge type junction, the dynamic resistance Rd (V- 〇), normal resistance RNN for tunnel type junction, tunnel type junction, and tunnel type junction.
is expressed by the relational expression. T is temperature and Tc is critical temperature. If we set Ro=ξRNN, then r=tori=Q-2--
−−−−−−・・−・・−・−(3) ξr ξr. 5QUID depending on the relationship between It and the magnitude of τ
The transition of the quantum state of is shown in Figure 2 (cl), It2 diagram (C
) The vertical axis in the middle is Is, and the horizontal axis is time. As can be seen from Fig. 2(c), when ΔtIv, the modulator l of Is
ΔI is the smallest.・One stone is . Therefore, Δi#vτ is the ideal condition,
From Equation (1) and Equation (2), the following equation is obtained.As can be seen from Equation (5), the clock frequency ν and β2 are inversely proportional. In other words, the faster the 158QUID circuit is driven with AC external magnetic flux, the less clearly the transition between each quantum state of the 5QUID will appear in the circulating current. Clock Ins (bipolar = 0.
5 GHz), deity 80%, 7" = 3 mV, and assuming that ΔI ξ: 1, β is approximately 17.
It is. Furthermore, if a bridge type junction with a small capacitance at the junction is used, assuming a Δ work value of ξ=100, for example, it becomes π(0.6%).

Next, a case will be described in which a current is supplied to the load Rt via the inductance L4i that is magnetically coupled to the 5QUID loop.

If the current flowing through the load loop t formed by connecting both ends of the load Rt and both ends of the inductance Lt is It, then I2~=M+Lν 00010041100.
．． 6) Is ′″″Trdt Here, Is is the current flowing through the 5QUID loop, or the mutual inductance, and is a coupling coefficient for M-=kq.

If Is in equation (6) or M,, -1(llz R1l, then when It is caused, the current flowing through Rt is 5QUIDt-
It is proportional to the flowing current Is. Moreover, this can be interpreted as a situation similar to the superconducting limit of Rt→0.

)lIz Rzl is Lzω)～ ・・・・・・・・・・・・・・・・・・・・・
...dt=0 during the operation period (when RIs is reached, and if it is shown in FIG. 2)
．． Even if it is a direct current, if the time constant t during the operating period is sufficiently short, the operating period will end before the direct current decays exponentially. This Tc
-((The mutual condition is 7-='L-DRt
If ω, then 1, lω)2πDRj ・・・・・・・・・・・・・・・
...(8).Since D is DAT and D#1, it can be seen that equation (8) has the same conditions as equation (7).

To summarize the above, if the condition of equation (7) or equation (8) is satisfied in both the operating period and non-operating period of Is having a trapezoidal waveform as shown in FIG. 2(b), A current with a similar trapezoidal waveform flows through L.

Next, the operation of the embodiment will be explained.

As mentioned above, a sine wave current Ip is applied to the input inductor Lp.
When flowing, the current Is induced in 5QUID/I/-B7
has a trapezoidal waveform as shown in FIG. 2(b). The amount of change in current π during the operation period when ∆ is expressed by equation (4). In addition, the data D is the maximum value of Ip t L p
It is determined by the magnetic coupling coefficient of Ll and the maximum current of the Josephson junction 6. and equation (7)
Alternatively, if the condition of equation (8) is satisfied, a trapezoidal waveform current as shown in FIG. 2(b) is induced in the load loop 8, and 5
Since the SQUID loop 7 and the load loop 8 are coupled to each other, the inductance of 5QUIf)<Ln+L
x) and load loop inductance L, effective equation (9)
Among them is the coupling coefficient between Lz and Lz. Formula (4).

The relationship between equations 3 and 11 is as follows: When the condition of equation (7) is satisfied, the gate bias current of each Josephson digital gate 3 in which the superconducting inductor L2 of N[C2 is wound is expressed by equation (10). If Ig, the maximum value of t is Iz (max)
= nIg, so equations (7), (9), (
10) Therefore, according to equation (5), β of the jsQUID loop
The value of the inductance Ll is determined by the formula αl)
+ Ll.

From equation (11) in which the value of L is limited, Ll<<Lz
Assuming that, the following inequality holds.

The analysis below uses actual numbers. ci=-2π 0.9. Ig=0.1mA, turns ratio N=100. R
=100゜n=100, then from equation (12) Lz
<<20nH. Therefore, if we set L z w l n H, then from equation (11) we get 0, which also matches the condition Lt==.
If you configure a circuit like the one shown in the wc1 diagram with the above element parameters, each digital circuit will have @2
Trapezoidal wave-shaped snow and mud flows as shown in Figure 3.

Also, if it is the effective inductance of 5QUID loose when including = (Lx + Lz) 1t - number of resistors in the load loop - 7, then dIs dIs dL! L"-=(L
t+Lz) +M ・・・・・・Old・・・(
13) Using equation 0 (]3) and equation (6), which yields dt dt dt , we get: The last term of this equation 04) can be ignored if the following condition is satisfied. This almost matches the premise of equation (11), so L'L'=*L
1+L, (1-k”) ・・・・・・・・・
・・・・・・・・・・・・(16) Therefore, the influence of the resistive load does not appear on the 5QUID loop.

The Josephson regiator of the present invention is capable of supplying a trapezoidal waveform W flow to each Josephson digital gate, and provides the following improvements over the conventional Ji1 Sephun regierator.

(1) Smaller fluctuations in the t-flow value during the operating period can be obtained than in the conventional diode regulator.

(2) The Josephson junction in the SQUID loop only instantaneously transitions to a resistance state, so the amount of heat generated is small.

Furthermore, since the single particle tunneling IV characteristic is not utilized unlike the conventional di-1 Cefson regierator, the current value fluctuation during the operation period does not deteriorate due to heat generation.

(3) Output HIgv of conventional jime sefunn regulator
g − ], therefore, if the critical current Ic of the Josephson digital gate deviates from its designed value, the optimum bias condition of Ig=αIc cannot be maintained.

Output h8QUID of the Gil Sefson regierator of the present invention
It is proportional to the maximum Josephson current value Io of the Josephson junction in the loop. Therefore, if the Josephson digital gate and the Josephson junction in the SQUID loop are fabricated under the same process conditions, they will deviate from their design values by similar proportions, ensuring that optimal bias conditions are maintained. .

〔Effect of the invention〕

As explained above, the present invention is an 8QUID nonlinear circular FI.
By extracting the I'M current using a superconducting load inductor and supplying it to the Josephson gate via a dropping resistor, the Josephson digital circuit can be operated extremely stably.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a simple embodiment of the present invention, and FIG. 2(a) is a single junction i! A characteristic diagram showing the relationship between the circulating current of a 3QUID and an external magnetic field.
Figure (C) is a partially enlarged view of Figure 2 (Q)), Figure 3 is a circuit diagram of a conventional regulator, and Figure 4 (a) is the I-V characteristic of a conventional di-1 Sefson regulator junction. , FIG. 4) is a diagram of input and output current waveforms of a conventional dicarbonate Sefson regierator. 1...Regiator junction, 2...Dropping resistance, 3...Digital Sefson digital gate, 4...Gate load resistance, 5...
...Power bus, 6...Joseph non-junction, 7.
...5QUID loop, 8...Load loop, 9...Input inductor, 10...
First superconducting inductor, 11...Second superconducting inductor, 12...Superconducting load inductor, 13 Agent: Susumu Uchihara, patent attorney.
-Year 2'yM CC) 3rd Figure 5 Kasumi Bus $4- Figure (d)

Claims (1)

[Claims] A superconducting quantum interferometer in which a Josephson junction, first and second superconducting inductors are connected in a ring shape, an input inductor magnetically coupled to the first superconducting inductor, and the second superconducting inductor. a superconducting load inductor magnetically coupled to the superconducting load inductor, and one or more superconducting load inductors connected in parallel and inserted between both terminals of the superconducting load inductor.
A Josephson regulator comprising a unit circuit including a Josephson gate and a series circuit of a dropping resistor.