Measurements of the dynamic input impedance of a dc SQUID

A planar picoamperemeter based on a superconducting quantum interferometer

“…In [9] by Clarke and Hilbert, the dependencies of Θ and Λ on the magnetic flux in the interferometer are measured and studied in detail. The values of the parameters of our interferometers are close to those of the interferometers considered in [8].…”

Microstrip direct current superconducting quantum interference device radio frequency amplifier: Noise data

“…A thorough theoretical treatment of the noise of SQUID amplifiers has been given by Clarke and coworkers, [14][15][16][17][18] Tesche, 19,20 and Koch. 21 They could show that when one takes into account all the voltage and current noise sources in the SQUID, the optimum noise temperature of a SQUID amplifier is given by T optN % (S V S J ) 1/2 x/2k B V U % 7 Tx/V U .…”

Strongly coupled, low noise dc-SQUID amplifiers

“…The involved time constants are in the order of the period of the Josephson oscillations and can have an effect in some, especially high-frequency, applications. Nevertheless, experiments on SQUIDs show much larger time delays on the input of the SQUID [65,66]. A possible explanation for this effect will be given in chapter 2.…”

“…(1.15) and (1.16), are usually also assumed real and independent of the frequency. Only for the dynamic inductance of the SQUID 1/G JΦ , a delay and thus an imaginary part is mentioned in literature [59,64,65]. This delay is, expressed in a simple way, caused by the shunt resistances connected in parallel to the SQUID inductance.…”

“…Typical values of the dynamic inductance 1/G JΦ are larger than the SQUID inductance, |G JΦ | L SQ 1 [59,65]. Note that this small-signal parameter can be both negative and positive, depending on the working point.…”