June 25, 2019 A paper from e-Si-Amp partners PTB published in the Review of Scientific Instruments has been selected as one of the most read editors highlights of 2017. Equivalent circuit for noise analysis of the ULCA The paper “Measurement of sub-picoampere direct currents with uncertainties below ten attoamperes” contains an in-depth analysis and characterisation of a new variant of the Ultrastable Low Current Amplifier optimised for measuring current smaller than a picoampere (10-12 ampere). Under these conditions the white/type A noise can be reduced using very high value resistors in the networks that determine the total transresistance gain, but the longer term stability of these networks must not be compromised. The paper also contains a demonstration of the use of these devices with a wiring assembly based in a pulse tube refrigerator system, where wiring noise has to be carefully controlled. Measurement of sub-picoampere direct currents with uncertainties below ten attoamperes C. Krause, D. Drung, and H. Scherer Review of Scientific Instruments 88, 024711 (2017); https://doi.org/10.1063/1.4975826
