Why charge time is independent of signal amplitude?

Charge time is independent of signal amplitude because the charging process primarily depends on the capacitance and resistance in the circuit rather than the voltage level of the signal. In a capacitor, the time constant, defined as the product of resistance (R) and capacitance (C), dictates how quickly it charges or discharges, regardless of the input voltage. Therefore, as long as the signal is above a certain threshold, the rate of charge remains consistent, making charge time invariant to amplitude changes.