Questions tagged [capacitor]

A fundamental electronic component that stores energy in an electric field, commonly used in filtering applications.

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4answers
1k views

What situation would you use flexible termination ceramic capacitors?

These capacitors from Kemet have flexible termination. The datasheet says it caters for applications where the board flexes and normal ceramic caps can fail. However, I fail to see a situation where ...
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4answers
1k views

What is the difference between a ceramic capacitor of the same dielectric, but different voltage rating?

What is the difference between a ceramic capacitor of the same dielectric, but different voltage rating? Would the lower voltage one have lower ESR or ESL? For example, X7R 10uF 4V as compared to ...
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LC circuit: can it act as an "AC battery"?

I am curious about a resonant LC circuit. Assuming a perfect inductor and capacitor, would it be possible to tap off the energy in the oscillations to use it as a battery? Literally, it would be an AC ...
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1answer
389 views

Airwave TX "BYPASS" capacitor

I'm using an Airwave 663 module. It's a 5.8GHz FM video + stereo audio transmitter module. Here is the datasheet: http://www.airwave.com.tw/specification/RF%20modules/AWM663TX.pdf It is apparent that ...
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5answers
944 views

What's the resistance of an electrolytic cap soldered in backwards?

I'm trying to debug a friend's AMP6 audio amp kit. It seems that an electrolytic smoothing cap on the output of a 5 V regulator has been soldered in backwards. This seems bad, but the component is ...
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5answers
7k views

Electrostatically charging a capacitor

By rubbing a cotton cloth along a PVC pole, static electricity is generated. How can this be used to charge a capacitor? http://home.earthlink.net/~lenyr/stat-gen.htm is what I'd like to do, but it ...
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2answers
888 views

Explain this circuit?

This is one of the circuits in the Electronics 9/10 class. The package did not explain how transistor combination worked and why the capacitor will reverse its current. Can you explain this circuit?...
12
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2answers
14k views

Does an ideal capacitor dissipate power?

On several circuit simulators I have seen capacitors with a "Power" figure. Also, I have wondered how capacitive power supplies work. Does an ideal, zero resistance, zero leakage, zero inductance ...
12
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5answers
4k views

Are decoupling caps necessary for analog ICs (e.g. LM339, LM324...)?

Often 100n to 1µF decoupling caps are placed across IC supply lines for digital logic. For analog circuitry, are decoupling caps necessary when the environment is also shared by microcontrollers and ...
11
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3answers
3k views

Voltage ratings of capacitors: ceramic vs electrolytic

Now I know when it comes to electrolytic capacitors it's usually good practice to use a voltage rating 1.5x - 2.5x the maximum rating you ever expect the capacitor to be exposed to, as the lifetime ...
14
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4answers
2k views

Ceramic or electrolytic capacitors for a switching buck regulator?

I'm using the LM2734Z (step-down DC/DC converter), which operates at 3 MHz. I'm using it to step down 4.8 V - 20 V down to 3.3 V +/-5%. Is it better to use ceramic capacitors or ...
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2answers
1k views

Capacitor to provide power to a circuit during a very small interruption

I need some help in figuring out what size capacitor I need, and if my idea will even work. I have a small remotely-controlled helicopter, and a very small camera. I am trying to record video while ...
29
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4answers
16k views

"Starter Kit for electronics" - What to buy?

I'm going to buy some things for back to the electronic world. Starting with an Resistor Assorted Kit. Need to buy some kits containing the most common capacitors and transistors... what to buy??? [...
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5answers
2k views

Capacitor behavior in oscillating circuit

I've been making my way through "MAKE: Electronics: Learning Through Discovery", but have gotten stuck on Experiment 11, where I am making an oscillating circuit. The book calls for a 2.2uF ...
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3answers
1k views

How can I handle a low power condition with PIC?

I am working on a project that uses a PIC24F mcu. The power to my pic is backed by a very large capacitor (1F). When there is a main power loss, I can sense that immediately via a port pin but the PIC ...
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4answers
102k views

How do I calculate how fast a capacitor will discharge?

Say I have a 1F capacitor that is charged up to 5V. Then say I connect the cap to a circuit that draws 10 mA of current when operating between 3 and 5 V. What equation would I use to calculate the ...
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1answer
472 views

Drawdio the sound is very very low :S?

im a beginner at electronics. im trying make an drawdio circuit with the instructions in the link below: http://www.ladyada.net/make/drawdio/drawdio2schem.png i have following components on the ...
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1answer
3k views

How do I calculate the peak output voltage of a capacitor differentiator?

How do I calculate the peak output voltage of a capacitor differentiator?
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9answers
100k views

Why use capacitors?

Why do you need to store the voltage for some time in a capacitor? I've always assumed circuits to work when you power it on and stop when you power it off. Why can't the whole circuit be drawn ...
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2answers
527 views

Using a super-cap with a PIC24F to keep time in case of supply failure

I want to use a 0.1F 5.5V supercap to keep time with a PIC24FJ64GA004 device. Does anyone have any idea on how to implement this? I was thinking of using the supercap on the +3.3V supply line and ...
12
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3answers
3k views

Capacitors and motors

Every RC car I've cannibalized has had a small ceramic capacitor soldered on to the contacts of the motors. What is the purpose of having this? What happens to the performance of the motor with out ...
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3answers
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Help with power-loss protection using capacitor

I designing a circuit will store log data to an SD card. The information will be coming form a parent circuit that this one plugs into. The parent circuit will supply 5V to my daughter card. The ...
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6answers
14k views

Frequency dependence of electrolytic capacitors

It's said that electrolytic capacitors behave as inductors at high frequencies, which is why we put small ceramic caps in parallel with them: Electrolytic, paper, or plastic film capacitors are a ...
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9answers
99k views

Blink an LED with just a capacitor?

Is it possible to blink an LED using just a capacitor? (and maybe a resistor). For example, if I want to LED to blink once every 2 seconds. Is that possible? I know it can be done with a 555 as well ...
28
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7answers
36k views

How to find the ESR of a capacitor

I am building a power supply circuit, and the switching regulator (L4963) calls for a low-ESR output capacitor. The capacitor in question is C3 of the evaluation board circuit. What does "low" mean? ...
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4answers
586 views

iPhone programmable caps

Anyone have any details on how to make a programmable capacitor? Is it some fancy op amp trick? EDIT: I suppose I should be more clear. The new iPhone 4 is having severe antenna problems, because ...
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10answers
41k views

What are some reasons to connect capacitors in series?

Usually you either combine capacitors in parallel because you want to increase the total capacitance while fitting the components in a certain shape/position, or you just combine capacitors by buying ...
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1answer
3k views

Isolation Transformers (Capacitive Coupling)

In my application I have an issue with ground loops and to solve this I require to have devices isolated from their drivers. The system operates with a 13.56MHz signal and a wide bandwidth is not of ...
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3answers
22k views

Maximum current and voltage of Small Ceramic Capacitors?

Small ceramic caps are nasty because their markings, such as ceramic monolithic leaded "104M"(yellow-brownish) and epoxy ceramic monolithic leaded "223", do not reveal max values. Since I do not know ...
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2answers
19k views

What does polarization mean in "polarized cap"?

Question emerged from my last question about small caps' markings, better to open new question so not become bloated. Heard term polarization in the context of light but not with caps. Googling ...
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4answers
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Various Small capacitors' markings?

Wikipedia explains the basics about the markings of capacitors, here. It lacks many markings most of which confuses me: Ceramic brown-yellowish cap 104 K5K (small ) --- what is the end "5K"? (...
213
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17answers
179k views

What is a decoupling capacitor and how do I know if I need one?

What is a decoupling capacitor (or smoothing capacitor as referred to in the link below)? How do I know if I need one and if so, what size and where it needs to go? This question mentions many ...
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8answers
69k views

Decoupling capacitors: what size and how many?

Lots of chips nowadays require smoothing capacitors between VCC and GND for proper function. Given that my projects run at all sorts of different voltage and current levels, I was wondering if anyone ...
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2answers
715 views

How does an LC network filter power?

The ATMEGA datasheet suggests filtering the ADC reference voltage with an LC network, in other words VCC - L - AREF - C - GND. How does the inductor smooth the voltage better than just a capacitor?
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2answers
4k views

Why is it ok to use polarized caps to remove DC offset from an audio input?

I've seen circuit diagrams that use a polarize electrolytic to remove DC offsets from an input audio signal. The cap is polarized. Why is this ok?
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4answers
502 views

Theory: With an AC circuit adding capacitors will cause the current trend towards leading

so if you add enough caps can you emulate what an inductor is doing, ie. Lead the current so far that it appears to be lagging? I assume this doesn't work, why not?
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5answers
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How to deal with a DC adapter with irregular voltage output?

Background information: I tried hard to get a Schmitt-trigger working, but it kept failing. By accident I figured out, that my AC-to-DC adapter produces a very irregular voltage output (I could hear ...
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11answers
217k views

What are the behaviors of capacitors and inductors at time t=0?

Do capacitors act as an open circuits or closed circuits at time t=0? Why? What about inductors? I tried it out, and what I got was this: Initially when I opened the switch, the capacitor acted like ...
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6answers
25k views

How to convert AC to DC

I am designing a circuit that needs to output 5VDC @ 1A. I'm trying to use a wall transformer to step the voltage down to 12VAC. The next step is the diode bridge and ripple capacitor. The ripple ...

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