So capacitors help alot to smooth everything.I need that.

Is there a way capacitors harm a circuit if you need a smooth clean voltage?

What happens if i have 5v powersupply and i put lots of various capacitors(ceramic,electrolytic,tantalum), all rated over 5v btw. ground and +5v?

Do i get a smooth stable clean signal or do i harm my circuit in some way?

Have capacitors no drawback appart from low ESR / charging discharging time?


I'm new to electronics 2 months ago i didn't even know what caps are for . Even if i replaced various caps on older electronic devices.

Now after reading some stuff about electronics i understood that caps are good.

Those "Batteries" that store energy & "linearize" the voltage output. All i needed to know is if there is a drawback.

I experiment atm with simple circuits , simple ic's and most examples on the web are capacitor less. Even if each IC's Vcc should have a CAP. Each button each pot each sensor.To linearize the voltage and protect from current rushes.

All i wanted to know was if there was some sort of drawback on those "simple" circuits.

Apparentely no. If you don't exceed the capacitance.

My question started with totally different words wich i deleted after

"The wall of text makes it less likely that people will answer your question"

Like i said i'm not an electronical engineer so many things aren't that logical for me, I also have no oscilloscope to check the correct value of the capacitors by myself. All i can do is to google and find an adeguate formula and base everything on that.

Said that i don't get all the downvotes.

I'm just trying to learn new stuff and compensate the missing measuring tools with the knowledge i get from my friend google and you guys.

Actually a simple answer like "yes more caps don't harm" would have ben enough.


closed as too broad by Fizz, Matt Young, PeterJ, Null, Daniel Grillo Oct 26 '15 at 10:23

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ This is basically an electronics degree course, not a question. \$\endgroup\$ – Brian Drummond Oct 23 '15 at 15:26
  • \$\begingroup\$ i'm happy with basic tips ,in detail about clean 3.3v,5v,12v signal at the powersource side and the relative circuits. \$\endgroup\$ – cocco Oct 23 '15 at 15:30
  • \$\begingroup\$ Can you simplify your question so you're asking a single question, such as "how do you decide what size decoupling capacitor to use"? You may find your individual questions have already been answered here, if you phrase them like that. \$\endgroup\$ – Nick Johnson Oct 23 '15 at 15:33
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    \$\begingroup\$ What is your specific question? If we all give you some tips, how will you choose which is the best answer? \$\endgroup\$ – The Photon Oct 23 '15 at 16:18
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    \$\begingroup\$ If the "old question" stuff is no longer needed to explain what you want answered, please delete it. The wall of text makes it less likely that people will answer your question. \$\endgroup\$ – The Photon Oct 23 '15 at 18:29

Yes you can use a capacitor to debounce a switch. You just have to make sure that the time constant for the capacitor is larger than the time it takes for the switch to stop bouncing. Basically, you want the switch to finish bouncing before the capacitor gets charged up to the HIGH threshold. Calculating the time constant is complicated because you would need to know the output impedance of whatever power source is charging the capacitor. It could also be affected by other things switching simultaneously in the circuit. It is probably best to figure that out experimentally. If the switch still bounces with a cap across it, add a bigger cap.

Yes you can use multiple capacitors on a power supply. When capacitors are in parallel, the total capacitance is the sum of the individual caps. Having a big capacitance between a power supply and ground makes the voltage more stable (up to the power limits of the supply), at the expense of needing the caps to charge up when the supply is first switched on.

On the importance of the size of a capacitor: In the majority of cases the precise value of the capacitor is not critically important. What is more important is the order of magnitude (uF, mF, nF...). That still doesn't mean you can just pop any capacitor into a circuit and expect it to work. The range of capacitor values you can buy right off the shelf spans 8+ orders of magnitude. You could probably get away with replacing a 10uF cap with a 5uF cap, but you probably can't replace it with a 10nF cap (3 orders of magnitude or 1000 times smaller). It really depends on what the capacitor is used for in the circuit. There are also some circuits where the value of the capacitor is is ciritical importance, such as oscillators and precise filters.

Capacitors do have passive energy loss. Every capacitor should specifiy an equivalent series resistance, or ESR. This is a series resistance due to the materials and construction of the capacitor. It's like having a little resistor in series with the capacitor. Any time current flows through the capacitor, a little bit of energy is lost as heat due to this resistance. Capacitors also leak charge. There is a leakage current that slowly discharges capacitors internally. Energy is lost there as well.

  • \$\begingroup\$ basically if the charging time is not important , multiple sizes&/samesized capacitors wouldn't harm a circuit if smoothness is needed. \$\endgroup\$ – cocco Oct 23 '15 at 16:10
  • \$\begingroup\$ caps don't create any type of interference? what about the ceramic ones (smd)... they create noise ... they oscillate sometimes. \$\endgroup\$ – cocco Oct 23 '15 at 16:12
  • \$\begingroup\$ A capacitor by itself doesn't create any noise (ignoring the thermal noise). Ceramic caps can produce noise because they are sensitive to vibration but these effects are usually small. If you have unwanted oscillations in your circuit it's usually because of feedback or a gain stage that is unstable. Capacitors can actually help to stabilize a gain stage. \$\endgroup\$ – Robert Stiffler Oct 23 '15 at 16:21
  • \$\begingroup\$ ESR is actually low compared to a linear voltage regulator or a high watt resistor itself... wich concludes to the point that its better to put random sized capacitor btw the vcc&gnd than putting none? so the more capacitors the more stable is the current. \$\endgroup\$ – cocco Oct 23 '15 at 16:52
  • \$\begingroup\$ ESR is usually pretty small but it's important in some high frequency stuff. You probably want a fairy large capacitor between Vcc and Gnd. This will stablize the voltage, not the current. \$\endgroup\$ – Robert Stiffler Oct 23 '15 at 17:18

What are some drawbacks of adding extra capacitors?

  1. Inrush current. This was alluded to in @RobertStiffler's answer. When your power supply first turns on, it will have to provide current to charge up all the capacitors connected to its output. Taken to an extreme, this could result in excess current demand and conceivably even damage the regulator or some other components.

  2. Reliability. Electrolytic capacitors, in particular, have limited lifetimes. But lifetime is a statistical thing. With more capacitors, you have more chances to have one part fail early. (On the other hand, you might increase the average lifetime due to reducing the ripple current through any one capacitor. It's a trade-off)

    Ceramic capacitors can also fail, often due to mechanical stress. Again, more capacitors means more possible points of failure.

    More capacitors also gives your assembly shop more chances to screw up, so it could also result in lower out-of-box yield for your product.

  3. Cost. More capacitors cost more money. They also take up more board area, making your PCB cost more.

  • \$\begingroup\$ inrush current is an important point. as i don't know how much current a cap can draw in a short time. lets say the 5v regulator 7805 .. the old one has 1A how many 1000uF 16v capacitors would you need to burn the regulator? \$\endgroup\$ – cocco Oct 23 '15 at 19:21
  • \$\begingroup\$ cost is relative to the products quality. As the answers suggest.. want noisefree circuit... you need more caps... look at those motherboards. There is a cap every 2mm. \$\endgroup\$ – cocco Oct 23 '15 at 19:58
  • \$\begingroup\$ The lifespan of capacitors is irrilevant at the point you realize that everyone changes their phone, pc or other electronic gadget every year. I salvaged most capacitors that i measured, work and use from electronic devices from the 19th century. they don't last long on commercial devices because they are always at the limit. i replaced caps on 3 old monitors all of them just right after 2 years with slightliy bigger caps they now are still working after 9 years. same happend on my AV Reciever. 5 caps where broken. changed all the array with higher voltage one and it works until then. \$\endgroup\$ – cocco Oct 23 '15 at 20:10
  • \$\begingroup\$ Is the Inrush current a real problem or only on circuits with really big 1000uF++ cap arrays? \$\endgroup\$ – cocco Oct 23 '15 at 20:15
  • \$\begingroup\$ @cocco, engineering is all about trade-offs. If these issues aren't important in your application, then by all means stuff every square mm of your board with extra bypassing. \$\endgroup\$ – The Photon Oct 23 '15 at 20:22

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