Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Applied Physics Letters

Power gain of a SQUID amplifier

Donald G. McDonald

Published Mar 1, 1984• 24 citations
Publisher

Abstract

The power gain of a dc superconducting quantum interference device (SQUID) amplifier, with tuned input and output circuits, is computed as a function of the current and magnetic biases. A gain of 20300 is found at 1.5 GHz and 3470 at 3.0 GHz, implying a frequency dependence to the gain of approximately ω−2. The gain, as derived from the resistively shunted junction model, is compared with the gain of a simplified model based on the dc magnetic response Vφ. This comparison shows that the Vφ description of the SQUID can lead to large errors.

DOI
10.1063/1.94801

Related papers

Microstrip superconducting quantum interference device amplifiers with submicron Josephson junctions: Enhanced gain at gigahertz frequencies

M. P. DeFeo, P. Bhupathi, K. Yu +4 more

We present measurements of an amplifier based on a dc superconducting quantum interference device (SQUID) with submicron Al–AlOx–Al Josephson junctions. The small junction size reduces their self-capacitance and allows for the use of relatively large resistive shunts while maintaining nonhysteretic operation. This leads to an enhancement of the SQUID transfer function compared to SQUIDs with micron-scale junctions. The device layout is modified from that of a conventional SQUID to allow for coupling signals into the amplifier with a substantial mutual inductance for a relatively short microstrip coil. Measurements at 310 mK exhibit gain of 32 dB at 1.55 GHz.

arXiv:1008.1036•Applied Physics Letters•Aug 30, 2010•11 citations

Microstrip Superconducting Quantum Interference Device Amplifiers with Submicron Josephson Junctions: Enhanced Gain at Gigahertz Frequencies

Plourde, Britton, M. P. DeFeo, P. Bhupathi +2 more

We present measurements of an amplifier based on a dc superconducting quantum interference device (SQUID) with submicron Al-AlOx-Al Josephson junctions. The small junction size reduces their self-capacitance and allows for the use of relatively large resistive shunts while maintaining nonhysteretic operation. This leads to an enhancement of the SQUID transfer function compared to SQUIDs with micron-scale junctions. The device layout is modified from that of a conventional SQUID to allow for coupling signals into the amplifier with a substantial mutual inductance for a relatively short microstrip coil. Measurements at 310 mK exhibit gain of 32 dB at 1.55 GHz.

•Aug 5, 2010•9 citations

Input impedance of an amplifier based on a dc superconducting quantum interference device

Claude Hilbert, John L. Clarke

The measured input impedance of an amplifier involving a coil tightly coupled to a dc superconducting quantum interference device (SQUID) is found to depend on the current and flux biases of the SQUID. Variations in the input inductance arise from the reflected dynamic inductance of the SQUID, and are in reasonable agreement with the predictions of an analog simulator. Variations in the input resistance, on the other hand, arise from feedback between the output of the SQUID and the input circuit, and are in approximate agreement with the predictions of a simple model.

Applied Physics Letters•Oct 1, 1984•15 citations

Gain characteristics of SQUID-based RF amplifiers depending on device parameters

Young Ho Lee, KK Yu, J-M Kim +4 more

Radio-frequency (RF) amplifiers based on direct current (DC) superconducting quantum interference device (SQUID) have low-noise performance for precision physics experiments. Gain curves of SQUID RF amplifiers depend on several parameters of the SQUID and operation conditions. We are developing SQUID RF amplifiers for application to measure very weak RF signals from ultra-low-temperature high-magnetic-field microwave cavity in axion search experiments. In this study, we designed, fabricated and characterized SQUID RF amplifiers with different SQUID parameters, such as number of input coil turn, shunt resistance value of the junction and coupling capacitance in the input coil, and compared the results.

Progress in Superconductivity and Cryogenics•Mar 1, 2019•1 citation

A DC SQUID amplifier with a novel tuning circuit

Tetsuya Takami, Takashi Noguchi, Koichi Hamanaka

The authors report a SQUID (superconducting quantum interference device) amplifier with a novel tuning circuit that can be easily coupled to a finite-impedance source. The SQUID amplifier is designed for a source impedance of 50 Omega and a signal frequency of nearly 150 MHz. The performance of the SQUID amplifier has been measured at 4.2 K. The measured gain and noise temperature of the SQUID amplifier are 20 dB and 0.7 K, respectively. A saturation temperature as high as 200 K at the input of the SQUID amplifier is achieved. It is concluded that this type of tuned SQUID amplifier is applicable to the IF (intermediate frequency) amplifier of the SIS (superconductor-insulator-semiconductor) receiver.>

IEEE Transactions on Magnetics•Mar 1, 1989•15 citations

Superconducting quantum interference device amplifiers with over 27 GHz of gain-bandwidth product operated in the 4–8 GHz frequency range

Lafe Spietz, K. D. Irwin, José Aumentado

We describe the performance of amplifiers in the 4–8 GHz range using direct current (dc) superconducting quantum interference devices (SQUIDs) in a lumped element configuration. We have used external impedance transformers to couple power into and out of the dc SQUIDs. By choosing appropriate values for coupling capacitors, resonator lengths and output component values, we have demonstrated useful gains in several frequency ranges with different bandwidths, showing over 27 GHz of power gain-bandwidth product. In this work, we describe our design for the 4–8 GHz range and present data demonstrating gain, bandwidth, dynamic range, and drift characteristics.

arXiv:0908.4250•Applied Physics Letters•Aug 31, 2009•30 citations
The power gain of a dc superconducting quantum interference device (SQUID) amplifier, with tuned input and output circuits, is computed as a function of the current and magnetic biases. A gain of 20300 is found at 1.5 GHz and 3470 at 3.0 GHz, implying a frequency dependence to the gain of approximately ω−2. The gain, as derived from the resistively shunted junction model, is compared with the gain of a simplified model based on the dc magnetic response Vφ. This comparison shows that the Vφ description of the SQUID can lead to large errors.
We present measurements of an amplifier based on a dc superconducting quantum interference device (SQUID) with submicron Al–AlOx–Al Josephson junctions. The small junction size reduces their self-capacitance and allows for the use of relatively large resistive shunts while maintaining nonhysteretic operation. This leads to an enhancement of the SQUID transfer function compared to SQUIDs with micron-scale junctions. The device layout is modified from that of a conventional SQUID to allow for coupling signals into the amplifier with a substantial mutual inductance for a relatively short microstrip coil. Measurements at 310 mK exhibit gain of 32 dB at 1.55 GHz.
We present measurements of an amplifier based on a dc superconducting quantum interference device (SQUID) with submicron Al-AlOx-Al Josephson junctions. The small junction size reduces their self-capacitance and allows for the use of relatively large resistive shunts while maintaining nonhysteretic operation. This leads to an enhancement of the SQUID transfer function compared to SQUIDs with micron-scale junctions. The device layout is modified from that of a conventional SQUID to allow for coupling signals into the amplifier with a substantial mutual inductance for a relatively short microstrip coil. Measurements at 310 mK exhibit gain of 32 dB at 1.55 GHz.
The measured input impedance of an amplifier involving a coil tightly coupled to a dc superconducting quantum interference device (SQUID) is found to depend on the current and flux biases of the SQUID. Variations in the input inductance arise from the reflected dynamic inductance of the SQUID, and are in reasonable agreement with the predictions of an analog simulator. Variations in the input resistance, on the other hand, arise from feedback between the output of the SQUID and the input circuit, and are in approximate agreement with the predictions of a simple model.
Radio-frequency (RF) amplifiers based on direct current (DC) superconducting quantum interference device (SQUID) have low-noise performance for precision physics experiments. Gain curves of SQUID RF amplifiers depend on several parameters of the SQUID and operation conditions. We are developing SQUID RF amplifiers for application to measure very weak RF signals from ultra-low-temperature high-magnetic-field microwave cavity in axion search experiments. In this study, we designed, fabricated and characterized SQUID RF amplifiers with different SQUID parameters, such as number of input coil turn, shunt resistance value of the junction and coupling capacitance in the input coil, and compared the results.
The authors report a SQUID (superconducting quantum interference device) amplifier with a novel tuning circuit that can be easily coupled to a finite-impedance source. The SQUID amplifier is designed for a source impedance of 50 Omega and a signal frequency of nearly 150 MHz. The performance of the SQUID amplifier has been measured at 4.2 K. The measured gain and noise temperature of the SQUID amplifier are 20 dB and 0.7 K, respectively. A saturation temperature as high as 200 K at the input of the SQUID amplifier is achieved. It is concluded that this type of tuned SQUID amplifier is applicable to the IF (intermediate frequency) amplifier of the SIS (superconductor-insulator-semiconductor) receiver.>
We describe the performance of amplifiers in the 4–8 GHz range using direct current (dc) superconducting quantum interference devices (SQUIDs) in a lumped element configuration. We have used external impedance transformers to couple power into and out of the dc SQUIDs. By choosing appropriate values for coupling capacitors, resonator lengths and output component values, we have demonstrated useful gains in several frequency ranges with different bandwidths, showing over 27 GHz of power gain-bandwidth product. In this work, we describe our design for the 4–8 GHz range and present data demonstrating gain, bandwidth, dynamic range, and drift characteristics.