| 摘要 |
In order to avoid the drift of the output voltage caused by input leakage currents and consequently permit quasi-static measuring operation in spite of immunity to overvoltages, at the output of the charge amplifier there is provided a circuit arrangement having a d.c. voltage amplifier, an A/D converter, D/A converter and resistor, which circuit automatically compensates for the input leakage currents before measurement in an adjusting phase by a current Ic generated by it and keeps this current constant during the subsequent measuring phase. With the aid of a further operational amplifier of the same type, arranged in the charge amplifier, the input leakage current can be roughly precompensated with regard to temperature influences, whereby the A/D converter only has to carry out a fine compensation and can correspondingly have a lower resolution.
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