Aluminum Electrolytic Capacitors
Aluminum Capacitors are capacitors that are composed of two rolled up strips of aluminum foil with a strip of absorbent paper between them which is soaked in an electrolyte solution- all this being sealed in a can.
Electrolytic capacitors cover the capacitance range of 0.1µF to 500,000µF.
They have a wide tolerance range, usually ±20% or more.
Temperature coefficients are also large, typically being 20% or more over the operating temperature range.
Working voltages range from 10V to 100V. Capacitors of a given value are made with three or more different voltages.
The leakage rate of electrolytics are high, so they tend to leak out a lot of current.
Electrolytic capacitors are polarized and must be connected with the correct orientation in a circuit. If the capacitor is connected the wrong way and power is applied, gas is formed inside the can and it will explode.
Electrolytics show appreciable change of capacitance with age and usage. If a capacitor is not used for some months its capacitance gradually decreases. It is restored if the circuit is switched on and voltage is placed across it for a period of time
Electrolytics are useful for storing charge, including smoothing the current from power supply units; thus, they function as power supply ripple filters. They are also used where a large pulse is to be generated such as in the starting circuits of flourescent lamps and photographic flashes. Other applications including audio coupling and bypassing.
Their wide tolerance and poor stability makes them unsuitable for timing and filtering circuits where high precision is necesssary. And aluminum electrolytic capacitors are not suited for high-frequency coupling applications due to poor isolation resistance and internal inductance. They leak badly, have bad tolerances, drift and high internal inductance, which limits them to low-frequency applications.
Electrolytic capacitors are popular because they provide high capacitance values in small packages at a reasonable cost.
They are heavily used in almost every kind of circuit, because they are cheap, readily available, and are good for storage of
large amounts of charge.
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