noob capacitor question

[Buellboy]

Hi all, please excuse the noobie question, but I've searched high and low for a definitive answer and have found very little. So the question is...
Can a plastic box type cap be substituted with a ceramic cap of the same value? It probably depends somewhat on the circuit, so lets say for a control board on a dc to ac inverter.

 

[audioguru]

A ceramic capacitor is excellent at high frequencies. A DC to AC inverter might operate at high frequencies. But a ceramic capacitor has a wide range for its value (its tolerance) and its value changes with temperature change so it makes an inaccurate frequency in an oscillator.

A metalized plastic film capacitor is in a plastic box or is an Oriental "green cap" in an epoxy drop shape and is very good for audio and can have a tight tolerance for an accurate oscillator frequency.

 

[killivolt]

I like the example.

But which ones are we talking about.

 

[audioguru]

Almost all audio coupling capacitors are PET metalized polyester film type.
I haven't seen paper or polystyrene capacitors for about 35 years.

 

[Buellboy]

This is for a board that controls the gates on a MOSFET inverter. dc to ac. I'm guessing that it would be pretty high frequency. So the ceramic caps are good with high freq but not precise enough? Ok. So are the box type and epoxy drop interchangeable? Having trouble finding the value I need in a box type.

 

[audioguru]

I buy EPCOS metalized film boxed capacitors usually in 5% tolerance and nearly any value that is made.

 

[Buellboy]

Where do you order from?

 

[killivolt]

I buy EPCOS metalized film boxed capacitors usually in 5% tolerance and nearly any value that is made.

I've seen these used before; when I work with a Military Contractor. The circuit boards were very robust.

 

[audioguru]

I like the small European Epcos ones instead of the larger Oriental "green caps".