We describe a calibration setup for the transresistance of lowcurrent amplifiers, based on the capacitancecharging method. The calibration can be per formed in the current range of typical interest for elec tron counting experiments. The setup implementation is simple and rugged, and is suitable to be embedded in larger experiments where the amplifier is employed. The calibration is traceable to units of capacitance and of time. The base relative accuracy of the implementation is in the 10 −5 range.

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The calibration of the transresistance gain of low-current dc amplifiers can be performed with the capacitance-charging method, where the calibration current is generated by a calibrated voltage ramp applied to a reference capacitor. The method is typically implemented with a purposely-built voltage source having a very low-frequency trapezoidal periodic waveform output. Here we propose a variation of the method based on a sinusoidal excitation, that can be provided by a commercial oscillator and therefore more easily implemented. Sampled sinusoidal input and output are processed with a seven-parameter sine-fitting algorithm. The comparison between calibration with sinusoidal and trapezoidal excitations is ongoing and will be presented at the Conference.