Understanding capacitor types and terminology - Page 1
Forum section: electronics / beginners

author: Willster
author_rank: Newbie
timestamp: December 08, 2016, 09:42:10 pm
content: Hello,I Just need to get my facts straight on the name and the job of each type of capacitor.Bypass capacitors bypass the power supply to absorb positive voltage spikes and supply voltage for when you have a negative voltage spike.Decoupling capacitors remove the ac from a signal.Coupling capacitors remove dc. Like dc offset or whatever.Filtering capacitors remove noise on the signal.Smoothing capacitors help get flat dc and usally found either side of voltage regulators.Bulk capacitors are like bypass capacitors but bigger and are found in the power supply and are used to charge up the bypass capacitors.Storage capacitors are used to temporary power when you remove a coin cell battery from an RTC circuit or for timing like in the 555 timers.Suppression capacitors come in x and y class and are used to reduce EMI.Have i got all the facts right? Am i missing anything or any other type? Does one type of capacitor have multiple names? etc are couple and decoupling caps types of filter caps?The thing is. If im right about the names and facts, people must be getting it confused or wrong because people always call everything a decoupling capacitors when they really mean bypass capacitors and visa versa. Also people mix up filter and smoothing all the time. I understand that capacitors can do both but if its either side of a regualtor it should be called a smoothing capacitor because thats its main purpose. Its really annoying. Same with people calling it bypass or decoupling when talking about removing noise from a signal. They should call it filtering.This is all really hard terminology for a young player like me haha.Thanks so much,Will Smith

author: TimFox
author_rank: Super Contributor
timestamp: December 08, 2016, 11:30:01 pm
content: The original meaning of a "decoupling" capacitor is a capacitor that reduces coupling between stages of a muilti-stage amplifier through the power supply connections. This is another term for a "bypass" capacitor in such an amplifier. One reduces the coupling by bypassing any AC component away from each stage.

author: AG6QR
author_rank: Frequent Contributor
timestamp: December 09, 2016, 12:35:20 am
content: These aren't different types of capacitors, they're different names for uses for capacitors. Different types would be categories like aluminum electrolytic, polystyrene, mica, ceramic, tantalum, etc.But the reason there seems to be some trouble with these categorizations is that the uses you list aren't mutually exclusive. If your goal is to remove AC noise in order to get flat DC, is the capacitor you put across the rail a decoupling capacitor, filtering capacitor, or smoothing capacitor? Does it matter?In signal processing, you may use a capacitor in two broad ways: Send a desired high frequency signal through the capacitor to a place where it's wanted while blocking DC and lower frequencies, or shunt an undesired higher frequency signal to ground while passing DC and lower frequencies. In the first case, you send your signal through a capacitor, in the second case, you put a capacitor across your signal. The first one is part of a high pass filter, and the second is part of a low pass filter. Many of your uses are very minor variations on high pass filters and low pass filters.There are other uses for capacitors, for example in combination with inductors to produce resonant circuits, or in combination with resistors for timing circuits. They can be used to create delays in feedback loops to turn an amplifier into an oscillator.Quote from: Willster on December 08, 2016, 09:42:10 pm