> Steve wrote:

>> I am designing low and high pass op amp (+/- 15V) based active filters
>> near 1 Hz that require capacitor values between 1 and 10 uF. Are
>> there any reasons to not use surface mount...

> PeteS wrote:
>

>> Steve wrote:

>>> I am designing low and high pass op amp (+/- 15V) based active filters
>>> near 1 Hz that require capacitor values between 1 and 10 uF. Are
>>> there any reasons to not use surface mount multilayer ceramic chip
>>> capacitors in such a design ? Is capacitance change with voltage an
>>> issue ? The filters will be used at room temperature with little
>>> temperature variation.
>>>
>>> Multilayer ceramic chip capacitors are available in values to 10 uF or
>>> higher with +/- 10%% tolerances and lead spacings of a few millimeters
>>> for $1. Is it better to use metalized polypropylene or metalized
>>> polyester even though they are more expensive and have much larger
>>> lead spacing (up to 1 inch) ? Examples inlcude Panasonic ECQ-E(B) or
>>> ECQ-E(F) series and Epcos MKT series, available at 5%% or even better
>>> tolerance.
>>>
>>> Thanks, ...

> joseph2k wrote:

>> PeteS wrote:
>>

>>> Steve wrote:

>>>> I am designing low and high pass op amp (+/- 15V) based active filters
>>>> near 1 Hz that require capacitor values between 1 and 10 uF. Are
>>>> there any reasons to not use surface mount multilayer ceramic chip
>>>> capacitors in such a design ? Is capacitance change with voltage an
>>>> issue ? The filters will be used at room temperature with little
>>>> temperature variation.
>>>>
>>>> Multilayer ceramic chip capacitors are available in values to 10 uF or
>>>> higher with +/- 10%% tolerances and lead spacings of a few millimeters
>>>> for $1. Is it better to use metalized polypropylene or metalized
>>>> polyester even though they are more expensive and have much larger
>>>> lead spacing (up to 1 inch) ? Examples inlcude Panasonic ECQ-E(B) or
>>>> ECQ-E(F) series and Epcos MKT series, available at 5%% or even better
>>>> tolerance.
>>>> ...

> A capacitor is tolerance rated separately for capacitance across
> temperature and across voltage.

> PeteS wrote:
>

>> A capacitor is tolerance rated separately for capacitance across
>> temperature and across voltage.

> (snip)
> Thanks for correcting my misunderstanding.
>
> I found a rough graph of the effect on page 3 of this Kemet application
> note:
> http://www.kemet.com/kemet/web/homepage/kechome.nsf/weben/9B4CE7C36CF87BBCCA2570.../$file/F3102_CE.pdf
>
>
> According to this, the X7R types do pretty well as long as you stay
> below about 30%% of rated voltage.