TY - JOUR

T1 - Ultra-low noise current meter for measuring quickly changing currents from attoampere to nanoampere

AU - Wendt, Cornelius

AU - Bohnhorst, Alexander

AU - Zimmermann, Stefan

AU - Kirk, Ansgar T.

N1 - Funding Information: The project “Femtoampere (fA) bis Mikroampere (μA) schnell erfassen – FUSE” is funded by the German Federal Ministry for Economic Affairs and Climate Action and the European Social Fund as part of the EXIST pro-gram (Grant Number: 03EFQNI090). The ACKISION GmbH was founded from this EXIST project with the goal of commercializing its results.

PY - 2022/12/25

Y1 - 2022/12/25

N2 - Low-noise current meters are usually designed using high value feedback resistors. However, a high resistance reduces the maximum measurable current at a given output voltage and the maximum bandwidth at a given parasitic capacitance. Capacitive transimpedance amplifiers integrating the current to be measured correspond to a nearly infinite resistance. Here, we present a novel active reset architecture for discharging the integration capacitor that eliminates the leakage currents and charge injection of the necessary switches. This enables a capacitive current meter achieving the noise current of an ideal resistive transimpedance amplifier with an ideal resistance of 650 GΩ, while the dynamic range, bandwidth and zero-point stability are orders of magnitude greater due to the capacitive operating principle. At a 3-dB bandwidth of 50 Hz, the noise current standard deviation is σ i = 2.6 fA with a dynamic range of six orders of magnitude from femto- to nanoamperes. Digitally adjusting the 3-dB bandwidth to 0.45 mHz for measuring direct currents reduces the noise by three orders of magnitude down to σ i = 8.7 aA, resulting in a dynamic range of nine orders of magnitude. This is possible due to an excellent zero-point stability within ± 25 aA without temperature or humidity compensation.

AB - Low-noise current meters are usually designed using high value feedback resistors. However, a high resistance reduces the maximum measurable current at a given output voltage and the maximum bandwidth at a given parasitic capacitance. Capacitive transimpedance amplifiers integrating the current to be measured correspond to a nearly infinite resistance. Here, we present a novel active reset architecture for discharging the integration capacitor that eliminates the leakage currents and charge injection of the necessary switches. This enables a capacitive current meter achieving the noise current of an ideal resistive transimpedance amplifier with an ideal resistance of 650 GΩ, while the dynamic range, bandwidth and zero-point stability are orders of magnitude greater due to the capacitive operating principle. At a 3-dB bandwidth of 50 Hz, the noise current standard deviation is σ i = 2.6 fA with a dynamic range of six orders of magnitude from femto- to nanoamperes. Digitally adjusting the 3-dB bandwidth to 0.45 mHz for measuring direct currents reduces the noise by three orders of magnitude down to σ i = 8.7 aA, resulting in a dynamic range of nine orders of magnitude. This is possible due to an excellent zero-point stability within ± 25 aA without temperature or humidity compensation.

KW - active reset circuit

KW - attoampere

KW - Capacitive current meter

KW - flame ionization detector

KW - gas chromatography

KW - ultra-low noise

UR - http://www.scopus.com/inward/record.url?scp=85143629684&partnerID=8YFLogxK

U2 - 10.1515/teme-2022-0049

DO - 10.1515/teme-2022-0049

M3 - Article

VL - 89

SP - 847

EP - 858

JO - tm - Technisches Messen

JF - tm - Technisches Messen

SN - 2196-7113

IS - 12

ER -