| 摘要 |
<p>The measuring of very low electric currents is performed by their integration into integration cycles with a time span of ti and measuring of the peak value of the saw-tooth voltage at the output of the integrated circuit each time at the end of the integration cycle, where from this saw-tooth voltage the voltage noise components, generated by an operational amplifier in the integrated circuit, featuring a frequency above the maximum frequency ranging to the size of (0.1 x 2 x pi x ti)exp-1, and from the filtered saw-tooth electric voltage the noise components, originating from the high-frequency voltage components of the aforementioned Johnson noise, which appear like an overlay distortion in the low-frequency part of the spectre of the saw-tooth electrical voltage, are filtered away. At the expense of reducing the direct as well as overlay component of the Johnson noise by the operational amplifier within the measurement circuit a higher absolute accuracy of the measurement is provided.</p> |
