| 摘要 |
An analog to digital converter includes a plurality of current sources selectively coupled to a capacitor for charging the capacitor from a reference level with a first reference current in a fixed time period and for discharging the capacitor with a second reference current to the reference level. The capacitor is then charged from the same reference level with a current derived from an unknown voltage source for the same period of time as in the case of the first reference current and discharged to that reference level at the same discharge rate by discharging with the second reference current. The difference between the respective times it takes the capacitor to discharge to the reference level in the two discharge cycles is determined and represents the amplitude of the unknown voltage. Suitable display means provide a digital representation of this amplitude. All the active digital and linear components can be formed on a single semiconductor chip using both PMOS and NMOS enhancement mode transistors in microcircuit form.
|
