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It is the time required to charge the capacitor, through the resistor, from an initial charge voltage of zero to approximately 63.2% of the value of an applied DC voltage, or to discharge the capacitor through the same resistor to approximately 36.8% of its initial charge voltage.
A discharged or partially charged capacitor appears as a short circuit to the source when the source voltage is higher than the potential of the capacitor. A fully discharged capacitor will take approximately 5 RC time periods to fully charge; during the charging period, instantaneous current can exceed steady-state current by a substantial ...
Once the capacitor's voltage drops below 1 ⁄ 3 V CC, the cycle repeats from step 1. During the first pulse, the capacitor charges from 0 V to 2 ⁄ 3 V CC, however, in later pulses, it only charges from 1 ⁄ 3 V CC to 2 ⁄ 3 V CC. Consequently, the first pulse has a longer high time interval compared to later pulses.
This time constant determines the charge/discharge time. A 100 F capacitor with an internal resistance of 30 mΩ for example, has a time constant of 0.03 • 100 = 3 s. After 3 seconds charging with a current limited only by internal resistance, the capacitor has 63.2% of full charge (or is discharged to 36.8% of full charge).
This charges or discharges the capacitor over time. Because the resistor and capacitor are connected to a virtual ground, the input current does not vary with capacitor charge, so a linear integration that works across all frequencies is achieved (unlike RC circuit § Integrator ).
When S 2 is closed (S 1 is open - they are never both closed at the same time), some of that charge is transferred out of the capacitor. Exactly how much charge gets transferred can't be determined without knowing what load is attached to the output. However, by definition, the charge remaining on capacitor can be expressed in terms of the ...
The lifetime specification for polymer capacitors is specified in similar terms to non-solid Al-e-caps with a time in hours at maximum voltage and temperature, for example: 2000h/105 °C. This value can be used for an estimation of an operational life time at individual conditions by a formula called "20-degree-rule": [72] [73] [74]
The time required to discharge a capacitor thus depends on what logic value is stored in the capacitor. A capacitor containing logic one begins to discharge when the voltage at the access transistor's gate terminal is above V CCP. If the capacitor contains a logic zero, it begins to discharge when the gate terminal voltage is above V TH. [41]