The pumpistor: a linearized model of a flux-pumped SQUID for use as a negative-resistance parametric amplifier

TL;DR

This paper introduces a linearized circuit model for flux-pumped SQUIDs, explaining their negative resistance behavior in parametric amplification and enabling better understanding and design of such devices.

Contribution

It presents a simplified, testable circuit model capturing the negative resistance phenomenon in flux-pumped SQUIDs for parametric amplification.

Findings

Negative resistance appears over specific phase ranges.

The model predicts device behavior in complex circuits.

Insights into frequency mixing effects in flux-driven SQUIDs.

Abstract

We describe a circuit model for a flux-driven SQUID. This is useful for developing insight into how these devices perform as active elements in parametric amplifiers. The key concept is that frequency mixing in a flux-pumped SQUID allows for the appearance of an effective negative resistance. In the three-wave, degenerate case treated here, a negative resistance appears only over a certain range of allowed input signal phase. This model readily lends itself to testable predictions of more complicated circuits.