Some of the most common applications and uses for electrolytic capacitors are: Contact online >>
Some of the most common applications and uses for electrolytic capacitors are:
Capacitors are one of the main components in all electronic devices and are vital to their operation. In modern electronics, you will most commonly find ceramic capacitors decoupling power supplies for almost every integrated circuit (IC) on a circuit board or aluminum electrolytic capacitors as bulk capacitance for a voltage regulator. However, capacitors are used in far more applications than just bypassing noise, and there are many more types of capacitors than only ceramic analog suppliers and aluminum electrolytic.
Different types of capacitors are used for:
In this article, we''re going to look at all the different types of capacitors, where they might be used, and common capacitor voltages. While we might think of capacitors as being a stable technology that hasn''t changed in decades, the reality is that capacitor today is very different from just a decade ago, never mind 20 years in the past. Applications you would never imagine using a certain type of capacitor for in the past are perfectly reasonable today with the advances in capacitor technology. In contrast, while some capacitors today might be thought of as obsolete with no practical applications compared to other capacitor types, they still have their niche applications at which they excel at.
Although all the different types of capacitors provide capacitance - they are not all equal. Capacitance is not the only critical parameter when selecting a capacitor, and each type of capacitor is used in different applications, so sometimes making the right choice is not an easy task. It would be best if you considered capacitance, maximum voltage, equivalent series resistance (ESR), equivalent series inductance (ESL), longevity, size, price, availability, parameters that change with temperature, and so on. For example, when choosing a bypass capacitor, the ESR and ESL parameters are essential. On the other hand, when choosing a capacitor for energy storage or sudden load change, current leakage can be more critical.
Choosing your capacitor primarily depends on your application and budget constraints. The price of capacitors can vary, from less than a cent to more than $100.
Let''s take a look at the capacitor types, where they are used, and when one is more suitable than another.
Ceramic capacitors are one of the most popular and common types of capacitors. In the early days, ceramic capacitors had very low capacitance, but nowadays, this is not the case. Multilayer ceramic capacitors (MLCC) are used extensively in circuits; their capacitance rating can reach hundreds of microfarads (µF). Modern ceramic capacitors can be used in place of other capacitor types for dated hardware/designs, such as electrolytic or tantalum. The difference between an electrolytic capacitor and a ceramic capacitor is the latter offers higher performance at a lower cost.
MLCCs have a ceramic dielectric body, which is a mixture of finely ground granules of para-electric or ferroelectric materials and other components to achieve the desired parameters. They have multiple layers of electrodes which create the capacitance. The ceramic is sintered at high temperatures to form the electrical and mechanical basis of the capacitor.
The ceramic layers are usually very thin; however, this depends on the voltage rating of the component. The higher the voltage, the greater the thickness and size of the capacitor for the same capacitance. The capacitor is usually protected from moisture and other contaminants by a thin coating.
MLCCs are not only popular because they are compact with relatively high capacitance, but also because they are critical for many applications where the electrolytic type would be completely unsuitable. As an often overlooked advantage, ceramic capacitors generally will not burst into flames or explode if you don''t treat them right. They do not have a polarity and can have voltages significantly beyond their ratings applied to them with no damage to the capacitor itself. In contrast, aluminum electrolytic and especially tantalum vs. ceramic capacitor have a tendency to turn into little rocket motors or explode if even a minor reverse voltage is applied to them, or their ratings are even slightly exceeded.
Other advantages of this type of capacitor:
There are two main classes of ceramic type of capacitors:Class 1: offers high stability and low losses for resonant circuit applications (NP0, P100, N33, N75, etc.).Class 2: offers high volumetric efficiency for buffer, bypass, and coupling applications (X7R, X5R, Y5V, Z5U, etc.).
Class 1 ceramic capacitors offer the highest stability and lowest losses. They have high tolerance and accuracy and are more stable with changes in voltage and temperature. Class 1 capacitors are suitable for use as oscillators, filters, and demanding audio applications.
The first character is a letter that indicates the significant figure of the change in capacitance over the temperature in ppm/°C. The second character is numeric and denotes the multiplier for the first character. The third character is a letter that represents the maximum error in ppm//°C.
For example: C0G ceramics offer one of the most stable capacitor dielectrics available. Capacitance change with temperature is 0 +/- 30ppm/°C, which is less than +/- 0.3% of the rated capacitance from -55°C to +125°C. The capacitance drift or hysteresis for C0G ceramics is negligible at less than ±0.05% versus up to ±2% for film capacitors.
The C0G (NP0) ceramic dielectric usually has a "Q" in excess of 1000 and shows little capacitance or "Q" changes with frequency. In addition to this, the dielectric absorption is typically less than 0.6%; this is similar to mica which is renowned for having very low absorption. This makes ceramic capacitors excellent for RF applications, and you can typically find ceramic capacitors which are specifically designed for RF circuits.
Class 2 ceramic capacitors have a much higher level of permittivity than those in class 1. This gives them a much higher capacitance level per unit of volume. However, as the tradeoff for this higher density, they have lower overall accuracy and stability. In addition to the lower precision and stability, class 2 ceramic capacitors also exhibit a non-linear temperature coefficient and a capacitance that is dependent, to a small degree, on the applied voltage.
Such capacitors are ideally suited to decoupling and coupling applications where the exact capacitance value is not critical, but where space may be an issue. They are also ideal for bulk capacitance on circuits that have rapidly varying loads, yet need to have a compact footprint, such as RF transmitter/transceiver ICs.
The first character is a letter that represents the low end of the operating temperature range. The second is the number and indicates the upper limit of operating temperature. The third character is a letter that denotes the capacitance change over the full operating temperature range.
One of the most common and popular classes 2 ceramic dielectrics is X7R which has a temperature range of −55°C to +125°C and a capacitance change of ±15% which is a relatively low cost yet still has relatively good tolerance. Y5V capacitors are also very common as the capacitance or voltage starts to reach the upper end of a given package. It has a temperature range of −30 to +85°C and tolerance across the range of +22/−82%, which is still suitable for many decoupling or bulk capacitance requirements that need to be compact and cost-effective.
Historically, there are also class 3 ceramic capacitors that offer high capacitance per unit of volume. These dielectrics are challenging to find still in production as modern class 2 multilayer ceramics can offer similar or higher capacitances combined with better performance in a more compact package.
Tantalum is a type of electrolytic capacitor that is made using tantalum metal as the anode, covered by a thin layer of oxide that acts as the dielectric. Tantalum offers a very thin dielectric layer which results in higher capacitance values per unit volume.
Tantalum capacitors are polarized, which means they are only able to be used with a DC supply and only placed in the correct orientation. A tantalum capacitor used outside of its rated voltage/temperature or with the incorrect polarity will rapidly lead to thermal runaway, causing fires and even small explosions. These can be mitigated by using safety components, such as current limiters or thermal fuses in your design. Still, it is something to be aware of when using tantalum capacitors near their ratings.
In comparison to ceramic capacitors, the equivalent series resistance of a tantalum capacitor is relatively high, typically orders of magnitude higher. This makes tantalum capacitors a poor choice for high-frequency applications.
Tantalum capacitors are typically significantly higher priced than MLCCs, so the usage of tantalum caps has become increasingly rare for general applications. They do have some outstanding features which make them ideal for certain applications, despite their additional cost.
Tantalum capacitors exhibit a linear capacitance change with temperature. This linear change makes it easier to calculate the capacitance under critical conditions. In addition to the linear change, the capacitance of tantalum capacitors rises with temperature, which offers advantages for energy storage or for switched-mode power supply load changing stability, for example. If a tantalum capacitor is close to a switched-mode power supply, its capacitance will rise slightly as the power supply comes under heavy load and heats up.
Due to the piezoelectric effect, ceramic types of capacitors are microphonic as they vibrate, generating voltages like a piezo microphone. This effect can cause additional noise in a circuit which is not ideal for boards in high-vibration environments with sensitive/low-voltage analog signals. This noise is not significant enough to affect digital or amplified analog signals, however unamplified analog signals from transducers or other very sensitive signals could be affected. This is one reason many audio-related components do not recommend ceramic capacitors. Tantalum capacitors do not tend to have piezoelectric/microphonic characteristics, which makes them ideal for audio applications, or applications that experience high vibration.
The permittivity of the dielectric in ceramic capacitors is due to the degradation over time of the polarised domains in ferroelectric dielectrics. While this might sound like a line of technobabble from a science fiction show, the real-world effect is a decreasing capacitance over time. Tantalum capacitors, on the other hand, tend to remain stable over their lifetime. Tantalum capacitors also do not dry out or degrade like aluminum electrolytic capacitors which makes tantalum capacitors ideal for long-life service applications, especially in scenarios where servicing is expensive or impossible, or where a device is mission-critical.
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