Questions tagged [capacitor]

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

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69 views

Powering multiple concurrently running micro DC motors

I have a small raspi controlled remote control car using regular drone motors such as these ones and tried using this 60w power supply unit that can be downregulated to 3v and connected everything ...
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174 views

Purpose of a capacitor placed between the ethernet signal?

I came across attached Ethernet design for one my application. Since connector used here is with internal MagJack support external transformer is not used, The PHY used here is AR8031 part. In the ...
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1answer
75 views

Figuring out the importance of each component in a circuit

This is the blueprint of a circuit that I've got to build on a breadboard, but I've a lot of questions regarding this. In the first part of the circuit, there is a V_cc of 10V, a diode D1, a LED D2, ...
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131 views

Why don't we use AC coupling caps for USB 2.0 [closed]

I see we have a requirement for AC caps on USB 3.0 running at 5 Gbps. But why not at USB 2.0 480 Mbps? My question is about why is there need for AC coupling caps on 3.0? Whereas none on USb 2.0 I ...
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96 views

Why do diplexer low-pass filter output have more inductors than capacitors and vice versa?

I am reading "Practical Radio Frequency Test & Measurement A Technician's Handbook" by Joseph J. Carr. On page 41, it has a diagram (figure 2.29 shown below). In that figure, why do ...
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470 views

Energy of capacitor

Hi readers, since energy stored in capacitor is given by the above formula. Does it mean if i use a voltage multiplier connected to capacitor, it will help to increase the maximum amount of energy ...
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1answer
78 views

Ceramic capacitor, does the size matter?

I am making a buck power supply and I need on the input and the output 4x 22uF @ >5V ceramic capacitor. Even at 10V I find plenty of cheap X5R MLCC in the sizes 0603, 0805 or 1206. By looking at ...
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1answer
98 views

From where can I get the impedance graph/ frequency response information of a capacitor?

I want to know the self resonant frequency (SRF) of a tantalum or aluminum capacitor. Is this usually supposed to be there in the datasheet? I am wondering why it is not mentioned in datasheet since ...
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1answer
185 views

Can I die from touching one capacitor lead?

Suppose I have a charged capacitor and I only touch one of the plates or leads. Will current start flowing through my body? I think yes, because there is an electric field between one plate and Earth/...
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64 views

Stop 'bouncing' input from float sensor

I'm trying to resolve an electro-mechanical issue to do with a water fill solenoid, that is triggered by a float valve. The problem is as the water approaches full, the float bounces causing the ...
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1answer
83 views

Which is the voltage on this capacitor?

I can't figure out the voltage on this 50uF capacitor. There are three values on it 420 V~ , 470V~, and 250VAC. Can someone tell me which it is? Thanks!!
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353 views

Following is an excerpt from a power electronics textbook. Is the statement true?

As far as I know ESR primarily depends on the type of dielectric. eg: Al electrolytic (higher capacitance value) would have much higher ESR than ceramic (usually lower capacitance value). Say for ...
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96 views

Jump in RC current response to a square wave

Periodic square wave feeding an RC circuit: I am currently studying RC filter response to a square wave input with a period of \$ T_1 + T_2 \$. I have understood about voltage expressions and current ...
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67 views

Capacitors: voltage-dependent capacitance?

While playing around with a capacitive power supplies, I observed some very weird behavior when passing a 60Hz sinusoidal current through a 1000V disk ceramic capacitor. The voltage curve was very ...
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135 views

What factors could have caused the ceramic capacitors on this board to crack?

While examining an old VGA card for faults under a microscope I found that all of the ceramic capacitors had cracked. The card is circa 1991 so it does have some age on it. But I wouldn't expect solid ...
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134 views

Can a Capacitor Recharge From Ambient Static Electricity?

We just had an OSHA trainer tell our group that a capacitor can be recharged by, I paraphrase, "ambient static electricity," thereby creating a potential hazard. Is this a documented ...
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33 views

Connecting a RC circuit to the output channel of an astable multivibrator (follow up question)

This is a question which I had asked earlier. Tinkering around, I found out that if I connect a capacitor to the load resistor, i.e. if I pass the output through a RC circuit, the voltage retains it ...
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79 views

How to calculate the discharged current of a capacitor from the discharge curve?

I observed the discharge of a capacitor on an energy harvester chip via an oscilloscope. The Output was used to power a BLE module. I know the capacitor value, discharge time, and the top and bottom ...
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87 views

Why do capacitors behave like this in Circuit Wizard? How is it in real life?

I recorded this video to show a situation in Circuit Wizard software. I am not sure what the right answer is. Can anybody explain is it exactly happening like this in real life , or just because it ...
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85 views

Can we use electrolytic capacitors on IC power rails?

Can we use bulk electrolytic capacitors on the power rails of an IC? I know that we will use bulk capacitors in switching regulators at input. Can anyone explain why or why not and how to find ripple ...
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20 views

What is the term Flc in LM27402?

Hi while going through LM27402 IC, inorder to find compensate components of cc1,cc2 and so on, there is term called Flc, can anyone explain what it is?
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44 views

Modelling ESR of a parallel plate capacitor

I am trying to model a parallel plate capacitor (on die capacitor generated using metal plates.) I know the capacitance per unit area, and metal sheet resistance. No knowledge of the dielectric. I ...
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1answer
76 views

Is the voltage rating printed on capacitors always DC?

Are there any cases where the voltage value printed on the capacitor is actually AC, like on film caps designed specifically for AC/Pulse operation? Or is the value printed on the capacitor always DC?
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39 views

Capacitor value on supply grid

I am using ATmega328p TQFP for application described in schematic. simulate this circuit – Schematic created using CircuitLab So there is plenty of load on output side (up to 500mA). I have ...
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1answer
68 views

How we select LC filter for MAX3221?

I have seen a schematic where they used MAX3221IPWRG4 (Texas Instruments), RS232 Driver and Receiver. There they have used LC filter of inductor value 0.68uH and capacitor value of 680pF, but in ...
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202 views

For the capacitor specification "Ripple Current at Low Frequency" is a higher value better for a linear power supply?

I'm finding information that seems to be contradictory in various places, and I think people are talking about different ways of looking at the same spec. The specification that Digikey uses to search/...
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1answer
68 views

How to use a battery charger evaluation module as a booster?

I have a power source that can give me around 0.9 ~ 1 V and 900uA. I would like to use the BQ25570 battery charger evaluation module to give an output of 1.8 V. I would like to attach a capacitor to ...
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142 views

12V relay with capacitor resistor - need some guidance

I am considering using the following example https://www.the12volt.com/relays/relaydiagram43.html to use a 12v relay to generate a pulsed ground. However I have zero experience with capacitors, ...
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112 views

Electrical destruction of MicroSD

I'm trying to design a device to store my private keys. I can't code in a way to just use some flash chips, so I thought I'd use a MicroSD card for the storage as a module. I intend to create a method ...
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1answer
66 views

Weird result when finding ripple bounds of RC circuit with square wave input

If \$V_{ext}\$ is applied to a RC circuit, then voltage across capacitor is given by: $$v(t) = V_{ext} + (V_i -V_{ext})e^{-t/RC} $$ Using above to find the ripple bounds \$v_l\$ and \$v_h\$, get two ...
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64 views

Are 555 PWM circuit resistor and capacitor values independent of the voltage applied to a 555?

I am new to electronics so my question sound dumb. I am using this diagram to build a 555 timer IC PWM circuit: The above circuit operates on 9V but I have 5V. Do I need to change capacitor and ...
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68 views

Capacitor on output of regulator causing short circuit

We were using switching regulator and when we turned on the regulator short was found. C285 was damaged. After removing C285 , regulator worked without any issues. We were suspecting inrush current ...
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1answer
79 views

How to choose the right value for a emitter cap for an RC oscillator?

I have a circuit like this: Given a low or a high impedance feedback network, how do I choose the right emitter cap value Ce? I know that the emitter cap depends on the impedance of the feedback ...
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91 views

What would happen if I inject the charges (ESD) at PCB many times and PCB is completely floated (isolated) from the earth?

Just I wonder: If I inject the charges (ESD) at PCB many times and PCB is completely floated (isolated) from the earth. Will charges be dissipated or remain? I think charges will be charged in the ...
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641 views

Current surge protection for relay contacts when closing

Here's a simplified diagram of a circuit I have: simulate this circuit – Schematic created using CircuitLab The battery is 24V. The relay is rated at 8A. My load draws 2A maximum. The ...
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2answers
145 views

Is a 350VDC capacitor safe for rectified 240VAC?

I need some capacitors to smooth out rectified mains (long story short, I see 50 Hz light flickering, so I need lights running on DC instead). While looking, I saw that 350V capacitors cost me only a ...
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80 views

Power supply filtering of ICs

My question is - why in 99% of designs we dont need to provide RC filter to the power supply of IC, just individual capacitor is required? I know, that paths does have some resistance, but still, the ...
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77 views

Antenna as part of deformed circuit

I have a basic question on my rudimental understanding on antennas. In this discussion or more precisely according to this answer essentially an antenna can be regarded as a part of deformed LC ...
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41 views

Route wire under the capacitor

There are caps in the red rectangular area. However, there is ground path between capacitor place holder. Those caps are used to filter high frq signal in the DC line. It would not degrade the ...
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Advantages of PML SMD Film cap from Rubycon over other SMD film caps?

SMD film caps like the WIMA SMD PPS line (with high capacitances of >1uF to ~10uF) are usually huge with 2220 to 6054 footprints. Does anyone know the tradeoffs of these Acrylic Rubycon PML film ...
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99 views

Desoldering capacitors - some get damaged and others don't

I was practicing desoldering components with a desoldering heat gun (Quick 861DW) of some boards I salvaged from a broken Sony Bravia HD-Ready monitor. I applied 400C air flow and used some flux on ...
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2answers
145 views

How to calculate efficiency of a rectifier with a capacitor filter

I was reading on rectifier circuits and I found out the efficiency of a center tapped transformer is the average power Pdc divided by the rms power Pac and if the resistance of the load is known then ...
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51 views

Capacitor banks with opposite polarities

How can the polarities be opposite? Source: Distribution Switchgear Professor A.T. Johns ISBN (10 digit) 0 85296 107 3 ISBN (13 digit) 978-0-85296-107-0
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Is it possible make capacitors discharge like batteries do?

This question is regarding the possibility of use of capacitors as batteries. One impediment in this is that the capacitor quickly discharges unevenly. But here's how a typical lithium ion battery ...
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3answers
146 views

Does a signal that doesn't change polarity charge a capacitor?

I'm wondering if a digital signal that does not change polarity charges a capacitor. If the signal has a frequency of 1 MHz, does that charge the capacitor faster? And if so, is it possible to ...
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77 views

AC analysis of circuit: capacitors in parallel with BJTs

It's been a while since I've done AC analysis for circuits, but the sources I've looked at say to short DC sources to GND, and to treat capacitors as shorts. Given the placement of C7, I think Q3 can ...
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186 views

Values at t=0- and t=0+ when closing switch; Circuit Analysis

I have a circuit as shown in the schematic and need to find out the values at t=0- and t=0+ but I don't understand it correctly. The condition is that the switch was open for a long time and closes at ...
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41 views

12 VDC test stand for 280 A (Start-up) @ 100 A continuous air compressor

I am working out a test stand that will use two Murata power supplies in parallel with this board to drive an air compressor rated at 100 A continuous and a start amp draw (momentary) of up to 280 A. ...
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265 views

dc offset removal

I want to manipulate dc offset of a signal. By using a RC filter, I can delete the dc offset when the cap is charged but there is some problem like frequency issue and long time constant. Any circuit ...
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Circuit modelling​ of a spherical conductor connected to a voltage source

A hollow conducting sphere is connected to a voltage source like this (below) For lumped circuit model of this configuration we need to know about its resistance and capacitance , although resistance ...