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Questions tagged [capacitor]

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

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Inrush current into capacitor bank

Given I am charging a 50uF film cap bank to 500V. Do I need a current limiting resistor or some sort of current regulator to minimize inrush current when i first turn on the power supply and/or limit ...
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39 views

Snubber capacitor VAC handling by frequency of C0G?

I'm looking for a suitable snubber capacitor (220 pf) for a boost converter. The semiconductor manufacturer recommends some ceramic capacitors for this http://www.mouser.com/ds/2/212/...
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99 views

THAT4315 audio analyzer - capacitors getting hot

I have designed a audio spectrum analyzer circuit with THAT4315 and a drivers for IN-13 bar graph nixie tube to visualize the signal level. To supply +-12V to the opamps, the Meanwell NSD15 module is ...
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70 views

Frequency dependent capacitor for AC sweep analysis in LTspice

I need to model a frequency dependent capacitor for AC sweep analysis in LTpsice. I see that it is possible for inductors with GLAPLACE component, but I don't find anything about capacitors. The value ...
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53 views

LTSpice capacitor network simulation question

Below is a circuit build in LTSpice. It is capacitor network simulation. What is of interest to me is the voltage at node N005. A voltage controlled switch rises the voltage of node N003 to 29.42 ...
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121 views

How can fully charge a capacitor without having it prematurely discharge?

I am looking to power a circuit using a 5.5V, 5F supercapacitor. I want to charge it to approx. 5V but I don't want it to discharge into my circuit until it has charged to 5V. I can do this by simply ...
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30 views

Class a amplifier load capacitance

What would happen in a class a amplifier if I connect a capacitor in series with the load resistor (between power supply and the transistor collector)? My goal was to block the dc qiescent current to ...
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70 views

How to make this circuit pass all conditions

I have this circuit (as part of a larger design): simulate this circuit – Schematic created using CircuitLab The resistors are with a tolerance of 1%. On the input, V1, the circuit gets a ...
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38 views

How to find voltage across resistors in RC Circuit with 2 voltage sources?

I've been struggling with this difficult RC circuit that asks for the voltage, Vo, across the R4 resistor. Edit: Assume that the switch has been opened for a long time, before it is closed at time t ...
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123 views

Finding total energy for RC discharged capacitor at t = ∞?

Most Rc circuits are not as severely difficult as this kind of circuit. I'm trying to solve for both the time constant and the voltage V2 across the R2 resistor, both of which will hold the necessary ...
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157 views

Ultracapacitors as a battery; how long will they last?

I would like a formula to be able to calculate how long it would take 6 2.7v 350f ultracapacitors connected in series to degrade from 14.4 volts to 11.5 volts given a parasitic draw of a specific load....
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57 views

What is this solar power RC circuit doing?

I am a CSE student working on a project. We are using a solar powered microcontroller. The solar panel's power goes through a fuse and an RC circuit with a varistor to the charging system. What ...
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36 views

RC circuit with pulse input voltage; finding the time constants

I've the following circuit: Question: What are the time constants of the voltage at node \$\text{Y}_2\$ when the up part of the puls comes and when the down part of the puls comes? MY WORK: The ...
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50 views

Will a start capacitor be damaged by an overloaded motor?

Background: A few days ago, the air conditioning unit at work began failing to start. Fans would turn, lights would be on, but no compressor start. I called a technician and he said the start ...
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2answers
70 views

Do I need decoupling capacitors when I'm PWMing an LED?

I'm a hobbyist (well, less than a hobbyist really) trying to layout my first PCB design. I'm somewhat familiar with the concept of decoupling capacitors. I'm fading 3 LEDs in and out (really, it's ...
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34 views

Behaviour of capacitor while charging

When a capacitor is applied with an AC Wave in a circuit containing only capacitor, it charges to its peak value between the time period of 0 to 90 degrees. My doubt is that what happens between the ...
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110 views

High frequency response of capacitors

I have studied the fact that the capacitor does not like a varying voltage across its terminals, and it acts as a short circuit initially so that there is no voltage drop across it. If this is true, ...
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41 views

how do i know if Vc(0+) or Vc(0-) is zero?

i mean like in this picture, why is Vc(0-) = 10 v? why isnt it =0? when do i decide that there exists a voltage there even though it was in steady state? im not completely getting it.
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49 views

How would I determine the ideal capacitor for a specific application

I am attempting to replace a Surface Mounted Multilayer Ceramic Capacitor in an Amiga A4000 which is described in a BOM as: Capacitor, SM, MLC, NPO, 100pF (1206) ...
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87 views

Charging a high voltage capacitor with power supply. How exactly?

I have a semi-serious hobby project with a couple of friends where we need to charge a pulse operated capacitor rated to around 4kV with 1500nF capacitance. For this I need a high voltage supply and ...
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63 views

Doing nodal analysis on a circuit with a capacitor.

I'm looking at with the switch open. I get While going through the nodal analysis I get V1 = 3V Does that mean current across the resistor would then just be 1mA?
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31 views

Boost Capacitor of Step-down converter

I'm working on the LT8607 Step-down converter to convert from 12V to 5V/500mA output. The circuit schematic is as below. What is the purpose of using the BST capacitor as shown in the schematic.
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25 views

How is Phase Shift of an Op-Amp calculated using Polar Coordinates

I have a textbook (Op-Amp: Characteristics & Applications by Robert G. Irvine, 1981) and its Frequency response chapter started by discussing the Internal LP filters between the Input Differential ...
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46 views

Is it acceptable to replace 2 parallel 100uF capacitors for LM2596 with two 220uF capacitors

I have a printer motherboard with the LM2596 IC. The older version of the motherboard had one 100uF capacitor at the output pin of LM2596 but LM2596 recommends that 220uF be used. Because a cheap ...
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12 views

Acronym for Conductive Polymer Al Solid capacitors?

Is there an universally understood acronym for that like elcap or mlcc? I've seen Poscon (POlymer Solid CONductive, presumably) being used, similar to Panasonic\$^{tm}\$ OS-CON\$^{tm}\$, which was the ...
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49 views

PSPICE simulation of capacitor voltage and current disagrees with math

I'm testing a simple enough circuit on PSPICE. The zener has a BV = 220V, so the capacitor has a voltage of 220V until the switch closes. Using the time equation for voltage of a capacitor: Vc(t) = ...
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62 views

Derivation of time constant for single source, single capacitor RC circuit

Take a circuit comprised of resistors, a single capacitor, and a single step response voltage source. Then: Every single voltage and current in the circuit, except at the voltage source, will have a *...
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2answers
60 views

Impedance-matched antenna with an extra capacitor

I'm looking at the a schematic for an ESP8285 module, and I am curious about what they are doing with the antenna. The module is the PSF-B85 (by ITEAD: the version with a chip antenna). The antenna is ...
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1answer
69 views

Decoding Ceramic Capacitor

How could I decode this capacitor? MEXICO is written on the other side and it's in a speaker.
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91 views

What is the function of this circuit? (Included an op-amp, capacitors and resistors)

What is the function of this circuit? What is the role of the C2 in Op-amp's input? This is probably a filter circuit but I am not sure.
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55 views

Time Constant of a Complex RC Circuit

I'm trying to model a diode as two capacitances, a conductance, and a series resistance, as shown here: In order to generate an expression for the capacitance I'm equating 1/w3db to the time constant ...
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2answers
98 views

Capacitor charging efficiency with a constant power source

I have a question. It is easy to derive the efficiency for loading a capacitor from a constant voltage or a constant current source, basically because exponential functions and constants are very, ...
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1answer
131 views

How to explain the reflected voltage on the oscilloscope when a pulse is sent through a transmission line with a capacitor at the load?

This is waveform that I got on the osciloscopewhen experimenting in the lab. A pulse was sent through the coaxial cable was used with a capacitor at the load. I have my own idea why is this happening ...
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87 views

Problem understanding an exercise regarding impulsions

So, I'm having quite some trouble understanding and solving the following exercise. We're given the following montage We are told that the following square signal (called Vin) is applied Now, we ...
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1answer
38 views

How to select the pulse capacitor?

I am trying to find information on pulse capacitors but there are too many options. Some vendor marked with metalized film capacitor,ceramic capacitor. In particular, I even don't know how to figure ...
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51 views

Calculate input impedance of this circuit

I'm not too sure about this. It says neglecting all other capacitances so then surely the Cgs capactior is zero and thus that connection from the gate to between the two caps is relevant. So isn't the ...
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1answer
144 views

Protecting a coin cell from high current spikes - using a capacitor or not?

I've built some prototypes and try to gather some data from them. Skip below the two horizontal lines to read more about it. Original Question Brief summary I would like to know whether it is ...
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49 views

What are the initial conditions used to find the coefficients in the current equations?

Suppose a RLC series circuit. R, L and C are in series with a battery and a switch. The switch is open. L and C are discharged. At t=0, the switch is closed and the battery (V1) feeds the circuit. I ...
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56 views

How do I find the current equations for the RLC Series Circuit?

Let's talk about a RLC series circuit. R, L and C are in series with a battery and a switch. The switch is open. L and C are discharged. At t=0, the switch is closed and the battery (V1) feeds the ...
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49 views

Admittance of the impedance of R and C in series?

I have a resistor \$R=150\$ and a capacitance \$C=\frac{1}{750\omega}\$ in series: \$ Z=R-jX=R-j\frac{1}{\omega C}=150-j750 \$ If I take the admittance I have \$Y=\frac{1}{Z}=\frac{1}{R-jX}=\frac{...
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160 views

Is this capacitor polarized?

I recovered a few capacitors of this style from an old cassette player. As far as I can tell, it seems like Mylar film, but the “100⊖” marking has me wondering. Is this some peculiar shaped tantalum ...
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73 views

What is the purpose of \$C_E\$ in this circuit?

I understand it acts like a filter for \$R_E\$, but what is the point?
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41 views

RC circuit with sinusoidal voltage - initial behavior?

For a simple RC circuit with a sinusoidal voltage source, the differential equation is: $$\frac{dq}{dt}=\frac{sin(t)}{R}-\frac{q}{RC}$$ When I plot the solution to this differential equation using ...
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3answers
67 views

Deenergizing Inductor

I am reading through "Practical Electronics for Inventors" and I came upon a chapter about deenergizing inductor. I understand the concept that when you cut the current going into inductor, it will ...
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1answer
87 views

USB 3.1 AC Coupling Capacitor Implementation

How should the AC coupling should be implemented when connecting a USB 3.1 hub to a USB Type-C connector through a MUX. Is it: Both sides of each MUX. On the switched output of each MUX. On the ...
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2answers
84 views

Voltage across capacitor in charging RC circuit with constant current source

simulate this circuit – Schematic created using CircuitLab I couldn't really figure out how to get the switch that I wanted but this is functionally the same. Before the switch flips, there's ...
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86 views
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295 views

Simple LED fade circuit

I've been looking for a simple LED fade in/fade out circuit when power is turned on/off for a 12 V LED. I have tried the following circuits but the problem is that I can't reach the full brightness of ...
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1answer
76 views

When I rework an SMD capacitor or resistor, it will sometimes stick to the soldering tip. Does this high temp then destroy it?

When I rework 0402 capacitors, then often stick to the tip of the soldering iron. My iron is set at 350. I then discard the cap because I am worried the sustained temp for a few seconds has destroyed ...
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1answer
48 views

What is the best approach to calculate the transfer function of this RC circuit?

I want to calculate the transfer function of the circuit below. I tried to calculate the equivalent impedance of each block and work my way with voltage dividers until I get to V3, but this method is ...