Polarized vs. Non Polarized Capacitors

When would you want to use a polarized cap versus a non polarized one and vice versa.

Usually, polarized capacitors would be used in DC applications while non-polarized in AC applications.

There are advantages and disadvantages for both, like polarized capacitors have a higher leakage current and act as a short-circuit when connected the wrong way. Also have a lower frequency response, but they are smaller than non-polarized capacitors of the same capacitance.

Also if you connect 2 identical polarized capacitors back to back with one of them reversed (e.q. (+-)_(-+) or (-+)_(+-)) you will get a non polarized capacitor with half the capacitance. This might be OK for a low frequency AC (Hz to kHz, maybe low MHz) application because you can end up saving space, but if you grow the frequency (MHz or with some capacitors GHz) you will definitely need a non-polarized capacitor.

For DC applications, like regulated voltage filtering, you can use polarized caps. Personally I use a combination of polarized and non-polarized capacitors for this particular purpose.

Errata: e.q. is actually e.g. and what I wanted to illustrate there was how to connect 2 polarized capacitors in series to obtain a non-polarized capacitor with half capacitance. ( and ) would have been the capacitor delimitations, + and - the polarities and _ the connection, so it should have looked like this:

( + - ) _ ( - + )

or

( - + ) _ ( + - )

Often when a capacitor style is chosen it will be based on things like capacitance value, series resistance, package size, voltage rating, etc. Not so much on whether it is polarized or not.

For example

I have used tantalum capacitors when designing my system decoupling. I chose some tantalum capacitors because they have a low series resistance. They are polarized capacitors, but that is not why I choose them.

I often includes some large bulk capacitors in my distribution system as well. They are often in the hundreds of micro-farad or mili-farad range. I usually choose electrolytic capacitors in this case because of the value to cost. These are also polarized capacitors.

I have also made many small rf filters in the past and for this I have needed some very small values pf to nf range. I have also needed them to have very small packages in the 0402 package range. in these cases I have chosen typical ceramic capacitors so I can get the size and value I am looking for. In these cases the capacitors are non-polarized.

where they are used

how are they in shape

Normally you use non polarised capacitors in applications such as loudspeaker crossovers
Polarised in smoothing decoupling of power supplies where ripple rejection is important

Strobes etc you might use non polarised capacitors or paper, polyester typical examples might be valve radio , valve amplifiers , rf equipment , transmitters etc

I am raising the ugly head of polarized capacitors vs. non-polarized that was discussed here years ago. But I am doing restoration, this time and old video analyzer. and still find a need for high voltage non-polarized which are now hard to find.
I am considering using two polarized as a substitute for the 20mfd@350v in a tube unit but the capacitor is in a video cicuit with a switchable pos/neg out. What is frequency limitation for this technique?