| 摘要 |
A sample and hold circuit uses two amplifiers the second being a Miller integrator and the first a comparator which compares the feed back stored capacitor voltage to the sampled voltage to bring the stored voltage of the capacitor to the sample voltage value. This stored voltage will have included in it the offset voltage of the first amplifier. However on readout this offset voltage is eliminated by disconnecting the sample input and also the connection between the output of the first amplifier and the input of the second and instead connecting the output of the first amplifier to the sample input and taking the output from this interconnection line. Since the noninverting or plus terminal of the first amplifier has impressed upon it the stored voltage of the capacitor the unwanted offset voltage is effectively subtracted. The foregoing sample and hold circuit also finds preferred use in a 12 bit recirculating A to D converter where cumulative offset errors would cause error. In such a configuration one of the sample and hold circuits can have the feedback interconnection of the first amplifier configured to perform suitable multiplication and subtraction, for example, for a Gray code. Here a second sample and hold circuit stores successive computational results.
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