| 摘要 |
A sample and hold detector is described which preferably includes a differential amplifier, a current mirror and a storage capacitor which is charged and discharged to the voltage level of an electrical input signal during appropriate sampling intervals. The differential amplifier receives the electrical input signal as one input and the capacitor voltage as a second input for generating, at first and second differential amplifier output ports, currents which are a function of the voltage difference between its inputs. To charge and discharge the capacitor, the latter is coupled to the differential amplifier's second output port via a current path, and the current mirror is coupled between the output ports of the differential amplifier for sourcing to the second output port a predetermined percentage of differential amplifier current generated at the first output port. The coupling among the current mirror, the differential amplifier and the capacitor is such that, when the signal input voltage exceeds the capacitor voltage, the current mirror charges the capacitor until the differential amplifier reaches equilibrium. At that point the capacitor voltage is a predetermined percentage of the signal input voltage. When the capacitor voltage exceeds the signal input voltage, the differential amplifier discharges the capacitor via the current path and the second output port until the capacitor voltage is a predetermined percentage of the signal input voltage, whereupon the differential amplifier's second output port receives all its current from the current mirror to the exclusion of discharge current from the capacitor. Hence, further discharge of the capacitor is precluded.
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