| 摘要 |
A sampling circuit is described which aims to obtain a sampled and held signal level determined in relation to a well-defined reference level VO even though the input signal is a wanted signal referenced to a barely stable reference level. This is particularly the case when sampling signals from charge-transfer photosensitive devices for which the obscurity level can vary. The structure includes a sample and hold (EB1) and a capacitor (C1) input, with a resetting circuit which periodically charges the capacitor (C1) to a value which is roughly equal to the difference between the input reference level (variable) and the output reference level (constant). The resetting circuit includes a looped amplifier (AD1) in which the loop (B1, EB2, B2) is designed to introduce a voltage level shift which is equal to the shift intrinsically introduced by the sample and hold (B1, EB1, B2).
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