A
aman
Guest
Can anybody please give me the difference between Bipolar and Non-polar
capacitors ?
capacitors ?
Navigation
Install the app
How to install the app on iOS
Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
More options
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
P
PeteS
Guest
Well, there are times one will use large capacitance that is
non-polarised. Note it's not because it's non-polarised, but because of
undesirable effects of electrolytics (and tantalums).
Large capacitance at a high voltage is the realm of electrolytics, of
course, and anything over about 100uF is too, but expect the high
values of ceramics to increase.
The issues with electrolytics (and to a certain extent tantalums, which
have other undesirable traits) is the high ESR (Effective series
resistance), their poor stability vs time and their horrendous
stability vs. temperature.
If you are filtering a large chip (let's say a power hungry processor),
it's distinctly possible there's up to 100A going on, but at 0.9 -
1.2V. As ripple performance is dominated by ESR, you need ultra low ESR
as well as some bulk. There are 100uF ceramics available at 6.3V that
are perfect for this sort of thing (and as the bulk output of power
supplies, replacing 1000s of uF of electrolytics) and they are cheaper
too. Of course, you could use bulk electrolytics with lots of small
ceramics, but you still don't get all the benefits of that ultra low
ESR as soon as you put an electrolytic in (it will still source/sink
the bulk currents).
As noted, switch mode power supplies are another example of where I
need low ESR (although it significantly complicates the loop stability,
but that's another issue) to maintain the output stable in the presence
of impulses, be they on input or output.
A bonus is the size - 100uF ceramics come in a 2220 case (0.22 x 0.2
inch) and very low height, and the fact they are MUCH cheaper than
electrolytics.
(One of the issues with tatalums is the chemistry involved - if they
overheat, they give off toxic fumes. One large company we OEMd
equipment for insisted we could never use electrolytics in the
equipment destined for them).
The following manufacturers make large ceramic values in MLCC
(MultiLayer Ceramic Capacitors) and there may be others:
Panasonic
TDK
Kemet
Cheers
PeteS
non-polarised. Note it's not because it's non-polarised, but because of
undesirable effects of electrolytics (and tantalums).
Large capacitance at a high voltage is the realm of electrolytics, of
course, and anything over about 100uF is too, but expect the high
values of ceramics to increase.
The issues with electrolytics (and to a certain extent tantalums, which
have other undesirable traits) is the high ESR (Effective series
resistance), their poor stability vs time and their horrendous
stability vs. temperature.
If you are filtering a large chip (let's say a power hungry processor),
it's distinctly possible there's up to 100A going on, but at 0.9 -
1.2V. As ripple performance is dominated by ESR, you need ultra low ESR
as well as some bulk. There are 100uF ceramics available at 6.3V that
are perfect for this sort of thing (and as the bulk output of power
supplies, replacing 1000s of uF of electrolytics) and they are cheaper
too. Of course, you could use bulk electrolytics with lots of small
ceramics, but you still don't get all the benefits of that ultra low
ESR as soon as you put an electrolytic in (it will still source/sink
the bulk currents).
As noted, switch mode power supplies are another example of where I
need low ESR (although it significantly complicates the loop stability,
but that's another issue) to maintain the output stable in the presence
of impulses, be they on input or output.
A bonus is the size - 100uF ceramics come in a 2220 case (0.22 x 0.2
inch) and very low height, and the fact they are MUCH cheaper than
electrolytics.
(One of the issues with tatalums is the chemistry involved - if they
overheat, they give off toxic fumes. One large company we OEMd
equipment for insisted we could never use electrolytics in the
equipment destined for them).
The following manufacturers make large ceramic values in MLCC
(MultiLayer Ceramic Capacitors) and there may be others:
Panasonic
TDK
Kemet
Cheers
PeteS