Low voltage sample and hold circuits

摘要

A very low voltage sampling circuit which is capable of a full ranging output when powered with a very low voltage, e.g., of about 1 volt. A pre-charge circuit is combined with a sample and hold circuit to avoid the need for low threshold switching devices in the sampling circuit, thus avoiding output droop due to the increased leakage of low threshold devices. The pre-charge circuit is placed between the sample and hold circuit and an output of the sampling circuit to 'boost' the voltage level of the output of the sample and hold circuit to above a predetermined threshold voltage level. The pre-charge circuit includes an output voltage boost capacitor which is charged before the hold cycle of the sampling circuit. The negative node of the output voltage boost capacitor is charged to a reference voltage based on a range of correction for the output voltage, and the positive node is charged approximately to a level of the input signal itself.