**Understanding Capacitors: A Comprehensive Guide**

In our quest to understand and harness the power of capacitors, it's essential to delve into their internal structure and properties. The first thing we notice about a capacitor is its capacitance, but as we dig deeper, we find that it also features a resistance and inductance. These are called Equivalent Series Resistance (ESR) and Equivalent Series Inductance (ESL), respectively.

**Equivalent Series Resistance and Inductance**

The ESR and ESL of a capacitor are parasitic components that arise from its internal structure. The big problem with these components is that they create power loss, which can have significant effects on the overall performance of our electronic systems. To understand this better, let's consider an example using a 100 Hz measurement taken by an LCR meter. This revealed a dissipation factor of 0.097, which indicates that the capacitor acts around 92% like a capacitor and 8% like a resistor.

**Dissipation Factor and Capacitor Frequency Response**

The dissipation factor is a critical parameter that describes the relation between the ESR and the capacitive reactance. As we increase the frequency of measurement, the dissipation factor increases because the dielectric ohmic value increases while the capacitive reactance decreases. This means that as frequency rises, the capacitor's impedance shifts more towards its resistive characteristics.

**Self-Resonant Frequency**

When the capacitive reactance equals the inductive reactance of the ESL, we reach the self-resonant frequency of the capacitor. Above this frequency, the capacitor acts more like an inductor than a capacitor, making it less suitable for applications where decoupling is crucial.

**Electrolytic vs. Film Capacitors**

The datasheet of an electrolytic capacitor reveals a dissipation factor that increases as frequency rises, indicating that it's better suited for ULF (Ultra Low Frequency) applications. On the other hand, film capacitors like the 150µF one feature a low dissipation factor, especially at higher frequencies. This makes them suitable for LF (Low Frequency) and MF (Medium Frequency) applications.

**Ceramic Capacitors: NP0 and X7R Classes**

For SMD (Surface Mount Device) ceramic capacitors, there exist different classes like NP0 and X7R. These two classes feature a different base material, which affects their stability over a wide temperature range. The NP0 class is more stable, while the X7R class has higher voltage-dependent capacitances.

**Practical Applications of Capacitors**

To demonstrate the importance of capacitors in real-world applications, let's consider an example using a 10µF capacitor. By checking its impedance with an LCR meter, we found that at 1 kHz, the dissipation factor was around 3%, and at 10 kHz, it was around 15%. While not as low as the film capacitor, this capacitance worked well for our MOSFET driver IC.

**Insulation Resistance and Leakage Current**

The datasheet of a capacitor provides more information about its performance, including insulation resistance and leakage current. These parameters are crucial in understanding the capacitor's ability to maintain isolation between its terminals.

**Conclusion and Further Reading**

In conclusion, understanding capacitors requires delving into their internal structure and properties. The ESR and ESL are critical components that affect the overall impedance of a capacitor. By recognizing these components and their effects, we can better choose the right capacitor for our applications. For more information on capacitors and their usage in various applications, I recommend checking out the webinar by The Würth Electronik eiSos Group.

WEBVTTKind: captionsLanguage: enRecently, I've been playing aroundwith some high power LEDs.To efficiently dim the brightness,I built up this simple test circuit,which features a function generatorto create an adjustable PWM signal,and n-channel MOSFET in series to the LED,to actually turn it on and off rapidly,and a TC4420 MOSFET driver ICto charge / discharge the power MOSFETs gatesas quickly as possible.Now in the low frequency rangeThis circuits dims the LED perfectly fineby changing the duty cycle of the PWM signal.But while for example using a frequency of 100 kHzand a duty cycle of 1%,The circuit works for a couple of minutes,but then randomly stops working.Because the MOSFET driver ICapparently destroyed itself.After replacing it. This circuit worked fine once againbut this time I examined the pins voltages of the ICwith my oscilloscope,to determine the culprits.And while probing the supply voltage pin of the IC,I noticed that there occurred 100 kHz oscillationswith peak voltages of 28V and 2VSince that is partly beyond the ICsmaximum supply voltage.It is no wonder that it self-destructs after a while.To solve this problem,The Würth Elektronik eiSos Group recently sent methree of their capacitor design kits.The General-Purpose DC Film Capacitors Design KitThe Multi-Layer Ceramic Chip Capacitors Design Kitand The Aluminum Electrolytic Capacitors Design Kit.So in this video,let's solve this mysterious IC supply voltage problem,and learn the differencebetween those three capacitor types,to find out which one you should use for which circuit.LET’SGET STARTED!This video is sponsoredby The Würth Elektronik eiSos Group.Let's start off with our MOSFET driver IC problem.The supply voltage breaks downand afterwards an oscillation occurs.This happens with a frequency of 100 kHz.Which not coincidentallyis the exact moment the power MOSFET gatesget charged up.So, if we break it downthe input signal (Vᴅᴅ) gets put high,which ultimately connects the gateof our power MOSFETs to the supply voltage.This action requires current for our IC.In order to power its own components,and ultimately charge up its own MOSFET gatesas quickly as possible.While observing this IC current through 1 ohm shunt.I noticed that it reached its first peak value of around 2Awithin only 15 nanoseconds.The only problem is that my power supply,due to its internal construction,is not the fastest acting energy source.That is why we can model its output impedanceas a small resistor in series with an inductor.Now if the IC would require a constant 1A,we would only get a small voltage dropacross the resistor,but no other problems!Since an inductor voltage droponly exists with a change in current flow.But since our IC wants to have 2A in a time of only 50ns,Our inductor now features a big voltage drop,which means we got a breakdownin the supply voltage of our IC.Combine that with a breadboard constructionwhich comes with noticeable parasitic capacitances,and we got ourself a small oscillatoron the supply voltage pin,that leads to problems.To solve that, we can add a capacitorin parallel to the supply voltage pin.Which is then often referred to as a bypassor decoupling capacitor.It's job is to basically providethe high current search for the IC,which the mains power supply can not offerbecause it is too slow.And thus it also suppresses noisefor other ICs in the circuits.The only question is:“What capacitor type is best suited for this job?”The two main ratings, you usually see on themis their capacitance and their withstand voltage.Now since all of my capacitor voltage ratingsare higher than the 12V I'm using,we should go for the highest capacitance rating.Right?I mean, since the capacitance rating is proportionalto the stored energy of the capacitor,we should definitely be ableto provide enough current with it.So I connected the 15,000μF electrolytic capacitorin parallel to the IC.And asserted that the oscillation peaksdecreased to 16V and 8V.Seems decent.Out of curiosity though.I also tried out a small 150µF film capacitoras a decoupling capacitor,which worked even better!By decreasing the peaks to 13V and 10VBut, why does such a puny small film capacitorwhose capacity is 100,000 times smallerthan the beefy electrolytic capacitor works better?Well, the reason is that while all capacitorsshare the same basic structurewhich means they got two metal electrodes,which are separated by a non conductive materialcalled the Dielectric,in order to create an electric fieldsand the store energy when a voltage is applied,their materials all differ.My electrolytic capacitors for example,use aluminum foil in combination with an electrolytes.While my film capacitors use polypropyleneand my ceramic capacitors use ... like the name impliesCeramic.This material choice influences electrical propertieslike the voltage or capacitance.But also other properties like for example,The expected lifetimeor whether a capacitor is flammableBut there are more hidden propertieswhich we can discover by examining the capacitorswith an LCR meter.(L: Inductance C: Capacitance R: Resistance)with an LCR meter.Sadly though the 15,000µF oneoverloaded the meter.But as a replacement,I used a 10µF onewhich works similarly as a decoupling capacitor.The first thing we notice is thatthe capacitor not only features a capacitancebut also a resistance and inductanceThose are called Equivalent Series Resistance(ESR)Those are called Equivalent Series Resistanceand Equivalent Series Inductance.(ESL)and Equivalent Series Inductance.And they do exist in a practical capacitordue to its internal structure.The big problem with that though is thatthe parasitic resistance creates a power loss.As an example, we can use the 100 Hz measurementof the LCR meter to determinea dissipation factor of 0.097.The dissipation factor describes the relationbetween the ESR and the capacitiveand inductive reactance.But let's neglect the inductive one for now.That means the overall impedance of our capacitoracts around 92% like a capacitorand 8% like a resistor.Which on the other hand means we waste energythat goes in and out of the capacitor as heatIf we increase the frequency to one kilohertzWe can see how the dissipation factor increasesto 0.220which means the capacitor now featuresan even bigger resistive components.With rising frequency this DF value increasesbecause the dielectric ohmic value increaseswhile the capacitive reactance decreaseswith rising frequency.It gets especially interestingwhen the capacitive reactance = the inductive reactanceof the ESLwhich happens at the self resonant frequencyof the capacitor.Above this frequency,the capacitor acts more like an inductorthan a capacitor.And thus, It’s not interesting for uswhen it comes to decoupling.Even the data sheets of the electrolytic capacitorgives us a dissipation factor of 16% at 120 Hzwhich means such electrolytic capacitorsare better suited for ULF applications(ULF: Ultra Low Frequency)are better suited for ULF applications.But if we insert the 150µF film capacitorinto the LCR meter.We can see that its dissipation factor is pretty much 0at 100 Hz and 1 kHz andOnly goes up to around 0.001So 0.1% at 10 kHzThe datasheet of the capacitorpretty much confirms those values.By giving a DF of only 0.26% at 100 kHzMeaning such film capacitorshave a very low ESL and ESR ratingand thus a high self resonant frequency.Which makes them suitable for LF & MF applications(LF: Low Frequency)Which makes them suitable for LF & MF applications(LF: Low Frequency MF: Medium Frequency)Which makes them suitable for LF & MF applicationslike our decoupling task.But we should not forget about our super tiny ceramicSMD capacitors.For which there apparently exists different classeslike NP0 and X7RIn a nutshell those two kinds feature a differentbase material.Which has the effect that class want ceramic capacitorslike the NP0 are very stableover a wide temperature rangewhile class two ceramic capacitors like the X7Rare not as stable over a wide temperature rangebut feature way higher voltage dependent capacitances.That makes class 1 ceramic capacitors perfectfor something like oscillatorswhile class two ones could be used for decoupling.Right?To find that outs, I grabbed the 10µF oneand checked it with my LCR meter.At 1 kHz, We got a dissipation factor of around 3%and at 10 kHz around 15% .So not as low as the film capacitor.But after soldering it to a THT breakout boardsand connecting it to my MOSFET driver IC.It reduced the oscillation to better valuesthan what the electrolytic capacitor offered.Now, of course a capacitor datasheetdepending on its typecan give us even more informationlike the insulation resistancewhich basically sits in parallelto the actual capacitance or the leakage current.Whose name pretty much speaks for itself.But you should now understand thatwhile electrolytic capacitorscan be used for buffering energywhich is why you see them often in power suppliesthey are generally not well suitedfor higher frequency filters or decoupling.And if you want more informationabout other applications of capacitorsand the usage of different capacitor types in general,then I highly recommend having a lookat the webinar of The Würth Electronik eiSos Groupwhich you can find in the video description.As always, thanks for watchingDon't forget to like share and subscribe.STAYCREATIVEAND I’LLSEE YOUNEXT TIME!(As alway, Subtitle by PolaX3)