can i use polymer capacitors in place of X7R ceramics?
any benefit to polymer over others?
thanks
any benefit to polymer over others?
thanks
how do polymer capacitors compare to ceramics?
- Thread starter joewales44
- Start date
led driver
50v
10uF
100k
50v
10uF
100k
no it's on supply voltage
Well I'm still kind of guessing, but ...
Generally ceramic capacitors will perform better at high frequency - behave more like capacitors and less like resistors and inductors. This is advantageous for filtering/controller radio frequency interference and being sure that fast-changing currents are not impeded. They usually have low equivalent series resistance (ESR) and can handle high ripple current. It used to be that a 10 µF 50 V ceramic cap was big and expensive. They are remarkably small and cheap now.
Good quality polymer caps (I'm assuming here we are talking about the solid dielectric "electrolytic" types) can come reasonably close to ceramics in high frequency performance, depending on capacitance. They may not handle quite as much ripple current and may be a bit higher in ESR, but you really have to look at specs carefully. They are more economical than ceramics for higher capacitances,
Ceramic caps, other than "C0G" types suffer from negative voltage coeffficient of capacitance. As the applied DC voltage goes up, the capacitance goes down. X7R aren't too bad for this, but it is a consideration in some circuits. Polymer caps don't have this problem.
Polymer caps are normally polarized, ceramics are not.
Ceramics may be able to operate reliably at higher temperature than polymer types.
Surface mount ceramics can be cracked if boards flex (board flex tolerant types are available). Polymer aren't going to have this problem.
The list goes on. You should be able to find some good information on the web. Much has been published on capacitor characteristics. There are many types and all have their pros and cons. You can spend a lot of time learning about capacitor properties. It is time well spent if you are doing power circuits, RF circuits or precision/high-performance analog circuits. You do need to keep all the details in your head. You already know enough to know there are differences, which is the important thing to start with. Be aware that both polymer and ceramic caps of today can be considerably better, one way or another, than they were a few years ago.
For your specific application, either would probably to do the job. Unless you have a lab full of good equipment, you probably won't be able to tell the difference in terms of performance - again if you are using good quality polymer types.
Where high-frequency performance is important, bad circuit layout can nullify some of the good properties of capacitors.
Generally ceramic capacitors will perform better at high frequency - behave more like capacitors and less like resistors and inductors. This is advantageous for filtering/controller radio frequency interference and being sure that fast-changing currents are not impeded. They usually have low equivalent series resistance (ESR) and can handle high ripple current. It used to be that a 10 µF 50 V ceramic cap was big and expensive. They are remarkably small and cheap now.
Good quality polymer caps (I'm assuming here we are talking about the solid dielectric "electrolytic" types) can come reasonably close to ceramics in high frequency performance, depending on capacitance. They may not handle quite as much ripple current and may be a bit higher in ESR, but you really have to look at specs carefully. They are more economical than ceramics for higher capacitances,
Ceramic caps, other than "C0G" types suffer from negative voltage coeffficient of capacitance. As the applied DC voltage goes up, the capacitance goes down. X7R aren't too bad for this, but it is a consideration in some circuits. Polymer caps don't have this problem.
Polymer caps are normally polarized, ceramics are not.
Ceramics may be able to operate reliably at higher temperature than polymer types.
Surface mount ceramics can be cracked if boards flex (board flex tolerant types are available). Polymer aren't going to have this problem.
The list goes on. You should be able to find some good information on the web. Much has been published on capacitor characteristics. There are many types and all have their pros and cons. You can spend a lot of time learning about capacitor properties. It is time well spent if you are doing power circuits, RF circuits or precision/high-performance analog circuits. You do need to keep all the details in your head. You already know enough to know there are differences, which is the important thing to start with. Be aware that both polymer and ceramic caps of today can be considerably better, one way or another, than they were a few years ago.
For your specific application, either would probably to do the job. Unless you have a lab full of good equipment, you probably won't be able to tell the difference in terms of performance - again if you are using good quality polymer types.
Where high-frequency performance is important, bad circuit layout can nullify some of the good properties of capacitors.
