# Capacitance and inductance of passive filter

1. Sep 14, 2008

### Idea04

I'm having some trouble calculating the values I need for a capacitor and inductor for a passive filter. The values that I know to use are current, voltage and frequency. But I have a voltage <1 volt and a frequency of 60Hz but no current. Can someone help me figure out what value of capacitor and inductor to use.

2. Sep 14, 2008

### dlgoff

You don't need to know the current. Just the frequency, capacitance and indunctance.
http://mysite.du.edu/~etuttle/electron/elect31.htm" [Broken]

Last edited by a moderator: May 3, 2017
3. Sep 15, 2008

### Idea04

Do you have an equation to figure out inductance and capacitance. If I don't have the capacitor or inductor how do I determine what the inductance and capacitance is. All I have is the frequency.

4. Sep 15, 2008

### f95toli

There is no equation; both are free parameters.
However, in real applications you need real componenents. If you take a look at what is available you will quickly realize that the range is actually quite limited; you can't buy a 100F capacitor or a 1 fH inductor. You need to find a combination of values that give you the right frequency and at the same time result in realistic values for C and L.

Which, by the way, can't really be done at 60Hz; for frequencies that low you need an active filter (unless you are willing to spend a LOT of money on the type of huge chokes used in e.g. tube amplifiers).

5. Sep 16, 2008

### Pumblechook

What sort of filter? For what? Low pass? Impedance? Roll off? Ultimate attenuation?

There are plenty of filter types .. Chebyshev, Butterworth, Elliptical, Constant K. These will have low passband ripple if terminated with the current i/p and o/p impedance.

There are probably on-line calculators to give you the component values.

Voltage and current only come into when considering the required power handling.