The capacitance needed to stabilize a voltage pulse depends on several factors such as the frequency and duration of the pulse, the load resistance, and the desired level of stabilization. In order to determine the appropriate value of the capacitor, it is important to calculate the time constant of the circuit, which is the product of the capacitance and the load resistance. This time constant should be at least 5 times larger than the duration of the pulse in order to effectively stabilize the voltage.
For a pulse voltage of 6mV and an LED load, a small value capacitor in the range of microfarads (µF) or even picofarads (pF) may be sufficient. However, it is recommended to perform further calculations or simulations to determine the exact value of the capacitor needed for your specific circuit.
Additionally, the type and quality of the capacitor can also affect its performance in stabilizing the voltage pulse. It is important to choose a capacitor with low equivalent series resistance (ESR) and high capacitance stability to ensure proper stabilization.
In conclusion, the value of the capacitor needed to stabilize a voltage pulse depends on various factors and should be carefully calculated or simulated to ensure optimal performance in powering your LED.