Subfemtoampere Resolved Ionization Current Measurements Using a High-Resistance Transimpedance Amplifier

Perspectives of the generation and measurement of small electric currents

“…However, a small-current range requires a set of high-value standard resistors, which are prone to instability over time and under environmental disturbances and tend to behave nonohmically in the low voltage range, as might be expected. Thus, if the nonlinearity in the range led by the Simplified diagram of the small-current measurement method based on a high-value standard resistor [18]. nonohmic behavior can be calibrated, the succinct measurement circuitry can be exploited, which facilitates real operation and provides robustness.…”

“…In contrast to the ohmic large-scale resistor network of ULCA, the National Metrology Institute of Japan, NMIJ/AIST, made use of a single stable high-value standard resistor (or a matching set of a couple of these resistors to compensate for their temperature coefficients) and has developed a small-current amplifier that can measure currents down to the 0.5 fA level [18]. A schematic of this current measurement system is shown in figure 7.…”

“…Therefore, the nonlinearity of the feedback resistors must be evaluated carefully in the small-current measurements with this system. Okazaki et al [18] clearly evaluated the nonlinearity of the feedback resistor made of a metal glaze thick film in the bias voltage range of 1 mV-100 V using another type of transimpedance amplifier (ULCA). The feedback resistor of 3 GΩ in ULCA is implemented as an array of thin-film resistors network, which mitigates the nonlinearity.…”

“…Colored data points depict conventional room-temperature methods, and black data points depict quantum-based methods. CONVENTIONAL ROOM-TEMPERATURE METHODS: Purple diagonal crosses ×: High-value resistor at AIST [18]. Orange open circles ⃝: ULCA at PTB [19].…”

“…Figure 7. Simplified diagram of the small-current measurement method based on a high-value standard resistor[18].…”