Temperature-stabilized differential amplifier for low-noise DC measurements

Abstract

A tabletop low-noise differential amplifier with a bandwidth of 100 kHz is presented. Low voltage drifts of the order of 100 nV/day are reached by thermally stabilizing relevant amplifier components. The input leakage current is below 100 fA. Input-stage errors are reduced by extensive circuitry. Voltage noise, current noise, input capacitance and input current are extraordinarily low. The input resistance is larger than 1 TΩ. The amplifiers were tested with and deployed for electrical transport measurements of quantum devices at cryogenic temperatures.

Anomalous Anisotropy in Superconducting Nanodiamond Films Induced by Crystallite Geometry

“…Various miniaturized SQUIDs are being developed for advanced applications such as mesoscopic magnetic imaging [35,36] and quantum information processing [37]. As the key components of the SQUIDs, the weak links were created by either generating deformations in superconducting microstructures [38], preparing a layered system where an insulator is sandwiched in between two superconductors [35,36], or making use of the boundary between biepitaxial superconducting films [37]. The as-grown grain boundaries and twin boundaries in our superconducting nanodiamond films provide the basis for the development of diamond-based scanning nano-SQUIDs.…”

Thermoelectricity in Quantum Hall Corbino Structures

“…The input impedance of this amplifier must be very high, because the internal resistance of the Corbino device diverges in the quantum Hall states. We use an amplifier with an input impedance of about 1 Tω [19]. Very little frequency dependence of the thermovoltage is found between f = 3 Hz and 100 Hz.…”

Charge-induced artifacts in non-local spin transport measurements: How to prevent spurious voltage signals

“…However, the output voltage V real out of a real differential amplifier also contains a contribution that is proportional to the average voltage of V + and V − that scales with the commonmode gain G CM [62,[66][67][68][69][70]:…”

“…Because of their high input bias currents in the nA or even µA range, amplifiers that use bipolar junction transistors (BJT) in their input stages are completely unsuitable for non-local spin measurements. But even amplifiers that use field-effect transistors (FET) with bias currents normally in the pA or even fA range [70] might cause problems, as a damage to the input stages may increase these currents significantly. It is a-priori not clear if the charge signal that is caused by input bias currents is relevant in a non-local spin measurement.…”