Questions tagged [capacitance]

Capacitance is the ability of a body to store an electrical charge

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can you give me sample problem with solution regarding transition and diffusion capacitance of a pn junction or diode?

I have already understand the concept of both. When a p-n junction is in reverse bias, the depletion region widens and forms a so called transition capacitance, and when the p-n junction is in a ...
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Buck converter input/ output capacitance

For a typical Buck (Step down), synchronous converter please consider the given image: I have added numbers there representing the following: Input voltage Input capacitance Output Inductance Output ...
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69 views

About smd capacitors values and voltage rating [closed]

My Dell 3542 (2014)laptopboard got failed...i tested the board,and i found 4 smd capacitors have fialure...there is no any thing on the board to inform me about the value or voltage rating of them ...
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Calculate the frequency corresponding to a given current or power attenuation in an LRC circuit

For a series LRC circuit, I'm trying to calculate the frequency corresponding to a given current (or power) attenuation to either side of the resonance frequency peak according to the formula for ...
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80 views

Miller Capacitance in MOSFET

The above image is regarding the Miller Capacitance present in the MOSFET. I am finding it tough to understand the concept of Miller capacitance. I am trying and researching documents and videos to ...
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1answer
74 views

what are the exact formulas for calculating the matrice elements Lo, Co, Ro, Go, Rs, Gd

The following code is a hspice code. what are the exact formulas for calculating the matrice elements Lo, Co, Ro, Go, Rs, Gd? In other words, I want Lo, Co, Ro, Go, Rs, and Gd calculation formulas. ...
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151 views

Capacitive moisture sensor not quite working

I have spent the past few days trying to reverse engineer a capacitive moisture sensor I ordered from eBay a while ago. The particular one I received looks like this: What fascinated me about this ...
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31 views

What determines the upper limit of the capacitive load on a DAC?

I need to drive a number of piezoelectric actuators. The AD5535B seems promising because of the high number of channels and low cost (and I happen to be able to borrow one for testing) but sadly, the ...
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1answer
54 views

Low capacitance diodes

I was reading the datasheet of DALC208 which is a low capacitance diode array. It is designed to protect components which are connected to data and transmission lines from over voltages caused by ...
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2answers
69 views

What is the capacitance of this Maytag fridge capacitor?

I have this capacitor in a Maytag fridge freezer. The fan stops when the fridge is on but works when the freezer alone is on. I am assuming the problem is the capacitor not bring able to boost power ...
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134 views

Can you get shocked if you touch a hot wire whilst perfectly electrically insulated?

Okay this issue has been bothering me immensely so hopefully someone will be able to help me out or steer me in the right direction. Lets say hypothetically I possessed an absolutely perfectly ...
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48 views

How to determine SMD capacitor rating

I am trying to fix my robotic sweeper, and I saw this highly suspect capacitor on the PCB, I presume it is gone and needs to be replaced. However I dont see any rating over this unit, so I am not ...
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5answers
154 views

How to emulate a capacitor discharge curve using a microcontroller output pin?

I require a configurable amount of capacitance, without using a bank of dozens of actual capacitors and some kind of complicated switchboard, like this: Not only would this be an unwieldy solution, ...
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1answer
57 views

Off Grid Storage Capacitor Calculations

I'm thinking about using a very large home made capacitor as an energy storage device for a light duty off grid application, running some led lights and some 500w loads for a few hours each evening. I'...
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1answer
76 views

Does a 4 pin smd crystal need external capacitors to work properly?

My understanding of how this works is quite poor, I've tried reading many sources but just got even more confused by the terms crystals, crystal resonators, ceramic resonators, oscillators, crystal ...
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1answer
64 views

In need for high variable capacitance

I am constructing a Chebishev or Butterworth audio filter (low and high pass), but I need to have all parameters highly adjustable - especially Fo and Q. For this purpose i would need to be able to ...
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29 views

Ac Fan motor capacitor value

I have a bad 350v 2 uf fan capacitor. I managed to find a 400v 6.3uf cap in my locality, would this work instead of the 2uf one? Thanks.
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783 views

Why does wire not have large capacitive reactance?

For capacitive reactance, I am presented this formula: $$X_C = -\frac{1}{2\pi fC} $$ Where clearly, the capacitive reactance is inversely proportional to the capacitance. This confuses me. We usually ...
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1answer
37 views

Can the capacitance of a proximity sensor be increase by adding layer to the capacitor?

Would adding layers to the capacitor of a proximity sensor from lets say 1 (A) to 4 layers (B) help with increasing the capacitance and at the same time the distance that can be sensed with a ...
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3answers
70 views

Capacitance of 2 angled conducting plates

I have to determine the capacitance of 2 conducting plate (fringe fields are ignored) with a certain area (5m^2 here) with a gap separating them (4mm here). The second plate is inclined at an angle of ...
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2answers
74 views

I need to measure the impedance of the system, is it better to measure the resistance or capacitance?

The goal of this project is to measure Retinol levels in the blood. To do this I will be use two electrodes, one of which will be coated in nanowires. These nanowires will then have antibodies that ...
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4answers
79 views

Analog circuitry for measuring capacitive touch

I'm interested in adding capacitive touch input to a project I'm working on. Ideally I would like a tapered shape so that a finger can slide up as if it's a mixing desk fader or something like that. ...
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1answer
53 views

Can you use 'Rubber,' Specifically Liquid Electrical Tape Between The Plates of a DIY Capacitor

The above is pretty much all there is to the question. By "can you," I mean will it be properly effective / are there any tips? If not, why? It seems that this ought to work, but I can't ...
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71 views

Capacitance of semi-cylindrical plates?

For a visual reference of what I mean by semi-cylindrical plates check the diagram below. EDIT: The above diagram is not what I intend to implement. It is just to show anyone trying to answer the ...
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1answer
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Why must USB low-speed devices use a captive cable?

The USB 2.0 spec says: "A low-speed device is required to have a captive cable." However, I can't find a good explanation for why this is the case. I have seen hints towards two possible ...
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1answer
66 views

What effect does the thickness of metal plates have on capacitance?

Clearly a decrease in thickness of the dielectric increases capacitance, but how about the metal plates on a parallel plate capacitor? If you increase or decrease the thickness too much will you see a ...
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Endless oscillator [closed]

Can we create an endless oscillator? simulate this circuit – Schematic created using CircuitLab The diodes will only allow a tiny current to move through the tank circuit-> the power loss ...
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1answer
44 views

Would bypass capacitors of a voltage regulator which powers an I2C device and the bus cause issues?

I'm planning on powering a 3.3V I2C sensor and its pull up resistors with a linear LDO regulator. http://www.farnell.com/datasheets/2108564.pdf The output of the LDO aswell as the sensor's power pins ...
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Can multimeter measure 3200µF if capacitance measuring range:10p…40n/400n/4µ/40µ/200µF?

A multimeter that has this specifications: Capacitance measuring range:10p...40n/400n/4µ/40µ/200µF will not be able to measure a 300µF or 3200µF capacitor? That's how it sounds, but I want to make ...
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23 views

Charge through a time-varying capacitor

If a capacitor has a time-varying capacitance, such that C(t) = C_0 + Kt, where K>0 is a constant. Then is charge-voltage relation, Q(t) = C(t)V(t) = (C_0 + Kt)V(t), valid? It should be noted that ...
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1answer
37 views

How is capacitance found when there are 2 different regions with dielectric in the in 2 parallel plate capacitors connected in series

The two capacitors are part of a capacitive pressure sensor, I am curious with reference to electrostatic theories how would capacitance be found in respect to the dielectrics. The two capacitors have ...
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Solve for junction capacitance from diode's SPICE parameters

I am trying to calculate maximum junction capacitance (or depletion capacitance) \$C_j\$ for the BAT62-02L diode from this datasheet based on its SPICE parameters: \$I_s=\$ IS \$=\$ Saturation ...
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122 views

How do capacitors in series work?

If capacitors are connected in series with a vltg source, then how would each plates get the polarity? For a single capacitor, the electrons from one plate are pumped by the source towards the other ...
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1answer
108 views

Measuring resistance with ohmmeter over resistor and capacitor in parallel

In "Teach Yourself Electricity and Electronics, 6th Ed." [Gibilisco] (2016) a test question reads as follows: A DC ohmmeter will give us a correct reading for a component in isolation (not ...
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73 views

How would you determine the Miller input and output capacitance for the amplifier in the figure?

When I calculate the Miller input and output capacitance I get; Cin(Miller) as 6.38pF and Cout(Miller) as 5.66pF. However, these values are incorrect.
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Button debounce ringing

I have a circuit where I am using a tactile switch to pull 3.3v down to ground and investigating debouncing the button. My relevant part of the circuit is The 100nF cap does work here my signal has ...
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1answer
46 views

Substituting a capacitor of different capacitance [duplicate]

If a circuit calls for a capacitor with a specific capacitance, what happens if a capacitor with a different capacitance is substituted? I have a circuit that calls for a 250uF capacitor to power a ...
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54 views

Isolation Capacitance (Cio)

How I can find a practical value of CIO barrier capacitance (primary to secondary side) in digital isolators?
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1answer
44 views

Calculate the capacitance equivalence in the circuit across terminals A and C

Greeting friends I am having some trouble to calculate the capacitance equivalence in this circuit due to the short circuit? Calculate the capacitance equivalence in the circuit across terminals A and ...
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33 views

How to calculate gate capacitances (Cgs,Cgd) of a GaN HEMT?

I have calculated Cgd and Cgs using an analytical model, And I found that the second one is negative for Vgs < Vth, where Vth is threshold voltage and Vgs is the applied voltage. could this be ...
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1answer
42 views

How to estimate I2C bus capacitance?

In my current project, I need a microcontroller to retrieve the temperature of 60 temperature sensors which are located on the same PCB with distances not exceeding 50 cm. The temperature sensor's ...
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1answer
27 views

How to control a capacitance control panel from a Raspberry Pi

I have a touch control panel with only one lead going to each "button" on the glass, it is not a full circuit only half of one. I have concluded if i ground one of the pins (ex: power), it senses and ...
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66 views

Why can't the equivalent capacitance be calculated like the method 2?

Question Three capacitor with \$C=100\mu F\$ and \$50V\$ are series connected,and connected with the \$10V\$ voltage source,what is the equivalent capacitance of this circuit? Method 1 \$C_{eq}=...
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1answer
41 views

How to measure small capacitance with high parallel resistance

I have a sensor that can be modeled as a capacitor and resistor in parallel. The problem with this sensor is the resistance is on the order of 10's MOhm and the capacitance (we believe) is single pFs. ...
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24 views

Capacitance modulation to maintain current-voltage (IV) character

The ideal capacitor DC analysis shows the time constant to be a function of the load resistance and capacitance. Since the load resistance will be constant during discharge, is there any research on ...
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1answer
143 views

Calculate Capacitance Value and Voltage Rating in the event of ESD Pulses

I have a input power filter circuit. It has ESD Protection capacitors which help to protect the downstream circuit from ESD Pulses. ESD Capacitors Specifications : C0001, C0002, C0003, C0004 = ...
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92 views

What is Bus capacitance in I2C? How it limits number of devices can be connected to the bus?

Bus capacitance limits number of devices that can be connected by I2C. What problem is encountered if one tries to exceed this limit can anyone explain this in detail please. Thank you
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What is the meaning of “400 kHz when other system delays permit?”

I am going through the datasheet of the P82B715 I2C extender. The datasheet says "400 kHz when other system delays permit." What does this mean? (In the Texas Instruments datasheet they do not ...
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58 views

Are there any effects on capacitance and inductance when operating at audio-frequency (i.e. 1kHz - 20kHz)?

At the moment, I study something about audio-frequency track circuits for railway applications and to understand its operation, an accurate model of such a circuit is required. The circuit of audio-...
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3answers
43 views

Why is a transmitter dipole's ends the max/min voltage instead of the middle?

If the AC voltage source is connected to the middle of the dipole, I'm confused on why the edges have the max/min voltage instead of the middle. In my mind, the middle of the dipole is closer to the ...

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