Guys, dc decoupling, ac decoupling and ac filtering capacitor are frequently used. How do we determine(select) the value of its capacitance?
1. All capacitors block DC in a series circuit.
2. Capacitors do not block AC, the relationship of capacitive impedance to frequency is Rc = 1/(2 * Pi * f * C)
3. On a brushed DC motor, a capacitor is frequently used to reduce brush noise and to some degree help limit voltage spikes. The value is typically small, 1uF or less with a high voltage rating (10 times supply voltage or more). In some cases two capacitors of different values are used, typically one in the low uF range and the other in the pF range. For some AC motors a capacitor is used for starting and/or running, you can read about them here: http://en.wikipedia.org/wiki/Motor_capacitor
1.When capacitor block dc, we call it coupling, right?How to determine the capacitance to block the dc?
2. When capacitor connected in parallel to ground, it short-circuited the ac to ground, we call it decoupling, right? How to determine the capacitance to short-circuit the ac?