polarized vs non, electrolytics

[tab a]

This may be too general a question, but: Can non-polarized electrolytics be substituted for polarized? One microF in this case, and Radio Shack has the non, but not the polarized.

This also leads to the question about substituting ceramics for electrolytics. An old thread says this is OK, but not the reverse?

Thanks.

 

[dknguyen]

I don't see a problem subbing bipolars for unipolars- it's just bipolars probably come in less sizes and smaller sizes, and cost more. But I'm almost positive that bipolars have a much smaller voltage rating than unipolars. If this is the case you may not be able to substitute. YOu have to make sure the voltage rating is enough for your circuit.

I also don't see a problem subbing electrolytics with ceramics. The main advantage of electrolytics over ceramics is that they can come in much larger sizes and are cheaper. You cannot sub electrolytics for ceramics (not always anyways) because ceramics are inhrently bipolar and can work at higher frequencies than electrolytics- so it may make the circuit ineffective, or make it explode if you blindly replace ceramics with electrolytics.

 

[eng1]

This may be too general a question, but: Can non-polarized electrolytics be substituted for polarized? One microF in this case, and Radio Shack has the non, but not the polarized.

1 uF (non polarized) polyester capacitor may be suitable for you application? Where do you use it?

This also leads to the question about substituting ceramics for electrolytics. An old thread says this is OK, but not the reverse?

Correct. But ceramic capacitors usually have values in the range of nanofarads and picofarads.

 

[tab a]

My texts were good at explaining the construction, cost and size issues but really didn't seem to have much to say about how you'd choose in those instances when you could get the same size cap in different types. I'm positive I don't understand it completely, but it is clearer.

Thanks.

 

[dch222]

It doesn't matter which you use provided that the circuit doesn't ever cause a voltage across the cap which is higher than its rating, and doesn't ever reverse polarity.

If polarity reversal is likely to occur, don't use an electolytic.

There is only a limited range of values (around 1uF) where both are readily available. Higher than this and it has to be electrolytic.

 

[dknguyen]

The type becomes critical in high frequency circuits when all the non-ideal characteristics of capacitors kick in. THere are also stability and lifetime differences, and different capacitors can fail differently (some worse, some better). There are also some differences with DC bias, etc.. You can Google for articles that outline it, as well as the applicaiton notes on www.avx.com.