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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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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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35 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
57 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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76 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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22 views

Dimmable 120V AC LED bulbs intermittent brown out?

I have 5 dimmable LED light bulbs hooked up through a common fixture to a dimmer. Roughly every minute or so, the bulbs will dim in unison slightly for about 1 second, the come back up. I have ...
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1answer
43 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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75 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
69 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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32 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
31 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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1answer
46 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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36 views

Can anyone help ID these Capacitors?

Can anyone help identify this (I think capacitor)? I’ve never seen this type on anything else but American Dynamics PTZ cameras. Some of them are have a C & number by them so I’m thinking it’s a ...
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1answer
100 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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1answer
32 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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1answer
43 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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54 views

Capacitor in series with diode

Hi, not sure if I'm getting this right. Current flows from the positive side of the AC voltage supply and charges up the capacitor, the capacitor cannot discharge as the diode is reverse biased. So ...
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1answer
41 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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1answer
154 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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21 views

Dynamic rolled-supercapacitor & Lorentz force & Induction?

I've been designing certain components that would have a supercapacitor attached to a movable (rotation/linear) element. The element is conductive and carries the current from (discharging state) the ...
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32 views

Ceiling fan capacitor replacement

Based in Australia with 240v mains supply. My ceiling fan capacitor blew it is a 450V 1.25microF (2 wire pic shown). Having trouble finding a replacement. The wall plate with 3 speed controller that ...
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57 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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37 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
63 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
55 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
59 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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78 views
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186 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
71 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
41 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 ...
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1answer
45 views

What is the purpose of these capacitors in this State Variable Filter schematic?

I need some help understanding this schematic. It's a state variable filter based parametric equalizer. What are the capacitors C4, C5 and C6 for? Are those coupling capacitors like C1 and C7? Are ...
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2answers
43 views

Little torque of single phase asynchronous motor

I have a single phase asynchronous motor rated 230V, 500W. It has three terminals labeled U, V, W. I connected L1 to U and N to V (other way round makes no difference though). Between V and W is a ...
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28 views

polarized capacitor in cadence schematic 9.2

I cant find polarized capacitor in cadence schematic 9.2. How to model s polarized capacitor in cadence schematic 9.2??
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2answers
70 views

Best Guesstimate for Capacitor Replacement [closed]

I'm repairing an old (circa 1960) console hifi system for my parents. I'm no expert but also not totally incompetent. It originally came from Sears, I do not know the model number, nor the power ...
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1answer
33 views

How to increase current output of capacitor bank with buck booster?

I'm pretty novice when it comes to electronics given that my background is in mechanical engineering. But I am trying to design a circuit that can take a 5V (almost 0A current) to charge a capacitor ...
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1answer
46 views

Charge Pump Circuit explaination

I am trying to understand a charge pump circuit here but one part has me scratching my head and this sort of scenario happens a lot with me in electronics. It’s a question of what happened first?? If ...
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27 views

Calculate the voltage of the capacitor as a function of the time

The current is a function of the time. At t<=0, it is 0, and for t=>0 it grows at a rate of 20 A/s. I was able to calculate the voltage of the resistor and the coil by myself. When calculating the ...
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1answer
90 views

Why does capacitor never fully discharge in this circuit?

I've found in the following circuit, when the value of RPD is very high (say 10MΩ), sometimes the capacitor actually never fully discharges and the mosfet stays partially on. The LED dims but never ...
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1answer
83 views

5-10 second backup for wifi router during power cut

In India power cut is often. And most houses are installed with Inver-battery, for backup till the power comes back. But since all inverters don't behave as ups, there occour a little gap between the ...
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31 views

Drone Ground Control Station Switchable Power Supply

My drone ground control station will be able to run off of a 12v power supply, or a 12v car battery. I want to make it so that if the power supply is plugged in and providing power to the load while ...
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2answers
93 views

Shorting capacitors using a transistor?

Introduction First off, I'd like to let you know I am a beginner at electronics so some of the stuff I say might be very wrong. What I want to make is a 'spark generator' for lighting some gases in ...
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1answer
62 views

Testing Capacitor in PWM Circuit with Oscilloscope Calibration Signal

I'd like to measure the effect of a capacitor in a PWM circuit with an oscilloscope. The capacitor is engaged on a switch connected to a DC motor. Can I hook the motor up to the 1 kHz calibration ...
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60 views

What value is this Capacitor (or is it a Varistor)?

What is the value of this capacitor? I can't recognize it as it's not a normal code. It's simply written "MC1301". Or could it be a Varistor instead? What do you think it is?
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1answer
61 views

replace ceramic capcacitor with electrolytic one

I need help, that i have a lack of ceramic capacitor value variety in my country. I need 47μF (microfarad) and 2.2μF (microfarad) ceramic capacitor and i can't get these values. So the question is,...
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1answer
306 views

How can I identify these capacitor values?

I’m trying to build the power supply from this schematic. I’ve been purchasing the parts, but am confused about the capacitors I’ve labeled, especially became their numbers start with “R”. What are ...
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68 views

Full bridge driver capacitor ringing problem

This is my first time designing a full bridge driver. I am experiencing problems with ringing on the output. I have made a pcb for it. This is a picture of the top side of the board. Backside Input ...
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3answers
79 views

Circuit analysis for RC circuit

I have this circuit and want to calculate the voltage at v2 when t>0. v1 has a 6 volt step at t=0. I tried to do nodal analysis and came to 2 equations for the 2 unknown nodes, but did not know what ...
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67 views

Weird behavior of the MLCC capacitor after soldering

It's my first time using this capacitor. Before soldering, the capacitance measured only around 6uF. But after soldering and desoldering, the capacitance became 9uF around, and stable. I tested ...
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2answers
106 views

Replacing a capacitor

I have an electronic device that I have had for a good few years meaning that it's no longer in warranty. Recently it has developed a fault where the device will turn itself off when more power is ...
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48 views

Can I replace polyester capacitor by ceramic in audio circuits?

I'm redesigning an amplifier circuit. I'm using the TEA2025B. In the circuit there are some polyester capacitors, I would like to know if there are problems in ...
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1answer
32 views

How to protect against a short circuit fail in 12VDC X capacitor?

When adding an X capacitor for simple line filtering in a 12V DC electronics project, how would you add protection against an unlikely short circuit failure in that capacitor? Is it as simple as a ...