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I was designing a circuit, I found a lot of datasheets that don't specify if the capacitor should be ceramic or electrolytic. So I started to wonder if the value of the capacitance would tell me the kind that should be used.

Is it true that when the capacitance is of nF or pF order, ceramic capacitors should be used and when the order is of uF, electrolytic ones should be used?

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    \$\begingroup\$ What are they for? Application matters more than size. \$\endgroup\$ – Matt Young Aug 23 '13 at 0:42
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    \$\begingroup\$ Application to be specified. Generally ceramics are more accurate (capacitance tolerance), good thermal(temperature) stability,can handle higher ripple currents, Lower losses(Low ESR). It depends on the application. for ex, Buck converters input capacitors needs to be ceramic,because input current contains more spikes, these caps reliable, damage cases are low. \$\endgroup\$ – user19579 Aug 23 '13 at 7:58
  • \$\begingroup\$ I'd love to know if there are any applications where internal construction details matter more than capacitance, voltage, ESR and size. Are there any uses that specifically exploit other characteristics? (polarity effects, temperature dependence, ...?) \$\endgroup\$ – RedGrittyBrick Aug 23 '13 at 8:49
  • \$\begingroup\$ @RedGrittyBrick I've seen hobbyist applications where the microphonic effects are exploited. In some cases, a mica or ceramic cap can actually work better as an ultrasonic mic sensor, than any but the expensive MEMS mics. I think I may have seen the polarity effect intentionally misused for some applications as well. Not sure about that last bit. \$\endgroup\$ – Anindo Ghosh Aug 23 '13 at 9:53
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I would have posted this as a comment if I had enough reputation for that.

As Peter Bennett points out, for capacitances < 1 µF ceramic is usually good while electrolytic is good for the rest. However, because of the higher inductance of large electrolytic capacitors they usually behave quite non-ideally for high frequency signals. To get a around this problem one can use an electrolytic capacitor in parallel with a ceramic capacitor. Then the electrolytic capacitor will provide good behavior for the low frequency part of the signal and the ceramic capacitor will provide good behavior for the high frequency part of the signal.

Example: You need a capacitance of 100 µF. Then, I would use one electrolytic capacitor of 100 µF in parallel with one ceramic capacitor of 1 µF. (That would provide a total capacitance of 101 µF, but capacitiors are usally much less accurate than within 1 % of the specified value anyways.)

Also, my (and Peter Bennets's) answers are only valid when you don't have any specific requirements due to the application you are working with (as user19579 points out in the comments of your question).

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Unless there is other evidence ("+" signs on the schematic, or different schematic symbols), I'd assume that 1 uF and smaller is ceramic, and over 1 uF is electrolytic (aluminum or tantalum). Electrolytics would usually have a voltage specified, but ceramics are unlikely to have a voltage specified - at least circuits operating under ~25 volts, as we can usually assume that any ceramic caps we can buy are at least 50 volts.

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    \$\begingroup\$ I frequently use ceramics up to 22 uF, but ones up to 100uF are easily available. The higher valued ceramics also tend to be lower voltage (down to 4 volts), and will/should always have the voltage specified. \$\endgroup\$ – user3624 Aug 23 '13 at 1:32
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    \$\begingroup\$ As David points out, this answer is just not applicable in the modern era - especially where surface mount devices are concerned. Multi-microfarad ceramics are common and cheap, but their voltage ratings cannot be ignored when you start placing them outside of the logic portion of a circuit. \$\endgroup\$ – Chris Stratton Aug 23 '13 at 3:40
  • \$\begingroup\$ Voltage ratings cannot be ignored, especially for smaller sizes and higher capacitances. For example this 47uF ceramic with a rating of 10V. \$\endgroup\$ – Damien Feb 22 '15 at 3:20

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