Electrolytic Capacitor: Types, Characteristics, Formula and Applications

Electrolytic capacitor is a type of capacitor that makes use of an electrolyte to facilitate a capacitance that is larger than other capacitor types. As compared to the ceramic capacitor, the electrolytic capacitor is known to have a much higher capacitance-voltage (cv) product per unit volume. Its large capacitance values make them particularly suitable for the purpose of passing and by-passing low-frequency signals and for storing large amounts of energy. Let’s have a closer look into the topic and discuss some important questions.

Key Takeaways: Electrolytic capacitor, Electrolyte, capacitor, capacitance, voltage, energy, low-frequency signals, anodization, oxide, cathode, anode, metal

Check also: Electrochemical Cells

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What is an Electrolytic Capacitor?

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An electrolytic capacitor is a polarized capacitor whose anode is made of a metal that forms an insulating oxide layer through anodization. This oxide layer acts as the dielectric of the capacitor. It is necessary to keep a higher voltage on the anode than cathode at all times. The failure of an electrolytic capacitor can be hazardous causing an explosion or fire.

Electrolytic Capacitor​

The video below explains this:

Electrolytic Capacitor Detailed Video Explanation:

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Construction Of Electrolytic Capacitor

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The electrolytic capacitor is constructed between two plates separated by an electrolyte, which consists of 2 terminals called Anode and Cathode. The oxidized layer covers these metals. this layer is the insulating material. Based on this material, there are three types of electrolytic capacitors: Aluminium electrolytic capacitors, Tantalum electrolytic capacitors, Niobium electrolytic capacitors.

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Types Of Electrolytic Capacitors

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There are 3-types of electrolytic capacitors which are as follows:

1. Aluminum electrolytic capacitors
2. Tantalum electrolytic capacitors
3. Niobium electrolytic capacitors

Aluminum Electrolytic Capacitor

• These capacitors are manufactured using foils of aluminum on which it is coated with oxide. the other material without coating is used as a cathode. there are two variants of this namely plain type and the other is etched type.
• The maximum voltage ranges from up to 500 v.
• The range of this capacitor ranges from 1mF to 47000 mF.

Aluminum Electrolytic Capacitor

Tantalum Electrolytic Capacitor

• The capacitor in which Tantalum pentoxide is used as an insulating layer is called a tantalum electrolytic capacitor.
• These are available in both dry and wet forms.
• One terminal is smaller than another one. The smaller one is made up of magnesium dioxide.
• They are more stable as compared to aluminum capacitors.
• The capacitance ranges from 47 nF to 470 microfarads.
• 50 volts is the maximum range of voltage.

Tantalum Electrolytic Capacitor

Niobium Oxide Electrolytic Capacitor

• The anode of this capacitor is made up of niobium monoxide.
• It works efficiently with DC voltages.

Niobium Oxide Electrolytic Capacitor

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Capacitance Of Electrolytic Capacitor

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The capacitance is formulated as a charge collected between dielectric divided by the voltage difference that exists across the capacitor.

C: measured in Farad

Q: measured in coulombs

V: measured in volts

Also Read: Electrostatic Potential and Capacitance Notes

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Characteristics of Capacitors

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Capacitance Drift: The electrical characteristics significantly depend on the type of electrolyte used and the anode. The capacitance of electrolytic capacitors possesses large tolerances up to 20% and recedes with time. It is possible to make Tantalum capacitors with high tolerances, but their maximum operating voltage is very low.

Insulation Resistance: The leakage current is generated as the DC Voltage is added to the capacitor. The insulation resistance is the ratio between these two.

Loss: Under the action of an electric field, the energy consumed by a capacitor due to heating in a unit of time is called loss. The losses of capacitors are mainly caused by dielectric loss, conductivity loss, and resistance of a part of the capacitor.

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Uses of Capacitors 

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• DC blocking: It prevents the flow of DC from passing and allows AC to pass.
• Coupling: it works as a connection between two circuits, allowing AC signals to pass through and be transmitted to the next circuit.
• Rectification: the semi-closed conductor switching element is turned on or off at a predetermined time.
• Energy storage: stores electrical energy for release when necessary, such as camera flash, hearing equipment, etc.
• Filtering: The capacitors used on graphics cards have this function.

Properties of Electrolytic Capacitor

1. Dielectric constant (K): the electrolytic capacitor also has a high dielectric; due to this it offers high capacitance values in reduced sizes.
2. Temperature limitation of electrolytic capacitor: As this capacitor contains electrolytic jelly inside it, it cannot be used below -40 degrees C and above 105 degrees Celsius.
3. Polarization of the capacitor: Electrolytic capacitors are always polarized. they should be connected in such a way that electrolyte is negatively connected
4. Cost-effective: the cost of the electrolytic capacitor is very low.
5. Size availability: it is available in various sizes from small ones to huge ones. that is why installation space is not an issue here.

Read more: Electrolytic Cells and Electrolysis

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Advantages Of Electrolytic Capacitor

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• Because of its high capacitance value, it is used where there is a high need to achieve more capacitance value.
• Among all, tantalum capacitors are more used because of their stability.
• It is useful in low-frequency applications.

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Disadvantages Of Electrolytic Capacitor

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• The capacitors must be used with a combination of nonelectrolyte capacitors to increase their size.
• As these capacitors possess polarity, attention should be given to making connections.
• It gets easily affected due to temperature changes.

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Applications of Electrolytic Capacitor

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• It is used to prevent voltage fluctuations in different filtering devices.
• It can be used in various filtering operations to reduce the ripple content in voltage.
• It can be used practically in audio amplification to reduce the “hums” in the circuit.

Read More:

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Things to Remember

• An electrolytic capacitor can be defined as a polarized capacitor whose anode is made of a metal that forms an insulating oxide layer through anodization.
• The electrolytic capacitor is constructed between two plates separated by an electrolyte, which consists of 2 terminals called anode and cathode.
• There are 3-types of electrolytic capacitors: Aluminum electrolytic capacitors, Tantalum electrolytic capacitors, Niobium electrolytic capacitors.
• The electrolytic capacitor also has a high dielectric; due to this, it offers high capacitance values in reduced sizes.
• Electrolytic capacitors are always polarized. they should be connected in such a way that electrolyte is negatively connected.