Generation of Reference DC Currents at 1 nA Level With the Capacitance-Charging Method

Abstract

The capacitance-charging method is a wellestablished and handy technique for the generation of dc current in the 100 pA range or lower. This method involves a capacitance standard and a sampling voltmeter, highly stable devices easy to calibrate, and it is robust and insensitive to the voltage burden of the instrument being calibrated. In this paper, we propose a range extender amplifier, which can be employed as a plug-in component in existing calibration setups, and allows the generation of currents in the 1 nA range. The extender has been employed in the Istituto Nazionale di Ricerca Metrologica setup and validated with two comparisons at 100 pA and 1 nA current levels. The calibration accuracy achieved on a top-class instrument is 5 × 10 −5 at 1 nA.

Calibration Setup for Ultralow-Current Transresistance Amplifiers

“…Equation (2) shows that the traceability of the measurement of R is given by C, a timebase, and a voltage ratio; therefore, absolute voltage traceability is not required. The method here proposed is a derivation of a method developed for the calibration of lowcurrent meters [16], [21], where a proper traceability of the v in measurement was however necessary.…”

“…The method here proposed is a derivation of a method developed for the calibration of lowcurrent meters [16], [21], where a proper traceability of the v in measurement was however necessary.…”

“…In the following, we describe a calibration setup for the transresistance gain of ultralowcurrent amplifiers based on the capacitancecharging method [14]- [21]. The method allows to produce accurate dc currents in the range 100fA to 100pA and is insensitive to non idealities of the input stage of current amplifiers, such as voltage burden and finite input resistance.…”

Comparison of Low DC Current Traceability Methods and Gas Capacitors AC–DC Dependence

“…2. The C-V source, extensively described in [2], [12], [13], is composed of a generator G providing a piecewise linear voltage ramp v in (t) = K v t. The ramp is fed to a capacitor C, which generates a current…”

Simple thermal control of dc low-current amplifiers improves stability

“…Most measurement setups, however, employ commercial room-temperature, high-gain (up to 10 13 Ω) transresistance amplifiers, calibrated (on-line or off-line) by a reference current generated either by the Ohm's law method [5][6][7][8] or the capacitance-charging method [9][10][11][12][13].…”