Reservoir margin asks whether the capacitor valley voltage stays above the required minimum after ripple is subtracted from the peak. The rows use exact capacitance and ripple ledgers; real reservoirs include capacitor tolerance, equivalent series resistance, load-current variation, mains timing, diode drops, and measured ripple uncertainty.
Capacitance controls whether the ripple valley reaches the regulator minimum. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Reservoir valley is peak minus ripple before the gate
The checked source has ripple two volts, so a ten-volt peak leaves an eight-volt valley. That exactly reaches the required minimum.
10V−2V=8V≥8V
Capacitance decides whether the same minimum is reached
The source peak, current, interval, and required minimum stay fixed. Only capacitance changes the ripple and therefore the valley gate.