Questions tagged [capacitance]

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

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951 views

Capacitive touch screen sensitivity question

I have a question about capacitive touch sensing. I have read a few related questions already (here, here and here) and I think I understand the basics. From my understanding, when a human uses a ...
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121 views

Parasitic capacitance of planar pcb coil

As an experiment I attempted to make a planar PCB coil as shown below: Showing parts of a single layer for presenting detail. Together with a an EE ferrite core it generated 85mH of inductance as ...
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1answer
88 views

Capacitance among N conductors

I would like to have a rough estimate of the capacitance per unit length of a system composed by N parallel identical straight wires. I tried to sketch the capacitance network but I'm able to solve it ...
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302 views

Formulas for Integral Components

Formulas for Integral Components: I am looking for "simple" approximative formulas for integral components. In particular for: A grounded interdigital capacitor (i.e. above a ground plane and with ...
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1answer
39 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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1answer
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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28 views

Sensing of AC current. Isolation Capacitor Problems?

I want to measure the AC Current flowing through a Piezocrystal (replaced in the circuit with a resistor) being driven by a TI DRV2700. http://www.ti.com/lit/ds/symlink/drv2700.pdf This Chip puts out ...
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65 views

Capacitance to digital converter for moisture measurement

I'm currently working on a irrigation system for which I would like to build a low cost soil moisture sensor. I would like to measure the moisture levels of a given environment based on a capacitance. ...
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175 views

How to reduce noise for arduino capacitive sensing

I have an artistically-painted 5mm-thick wood panel that I want to use as a light switch without alteration to the image. My solution was to (try to) make a specific region on the panel touch-...
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367 views

Load capacitance of the crystal: what is the practical difference between devices?

There's a lot of info and guides on how to select and calculate load capacitors for the parallel resonant circuits. They all assume that people do already possess crystal, and know its CL. That CL ...
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1answer
33 views

Capacitance to useful signal conversion

Working on a project, where we need to measure the change in capacitance(capacitance change roughly from 0.5 pF at the start, to 20 pF at the end of the measurement). On the variable cap, only the ...
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0answers
237 views

Moving a capacitor in a time varying or non-time varying magnetic field?

1) If a simple parallel plate capacitor connected to a circuit, and discharging, were to move in an exterior magnetic field, what would happen to the interior region? Interior region components: ...
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107 views

Measuring a small distance via capacitance

I am interested in measuring a small \$d\$ between two objects shown below by measuring the capacitance between the Terminals denoted as T0 and T1: The distance \$d\$ is roughly 1mm +/- 0.5mm ...
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72 views

Finding equivalent capacitance and resistance from DC circuit with combinations of R and C

In order to get the simplest RC circuit and get equivalent circuit tau: How can be its transient studied if before t = 0 there only exists one resistive part of circuit? I's obvious that before t = ...
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1answer
159 views

Selecting true crystal settings for 328P [7.3728 MHz]

I want to make a new board working with 115200 (gsm modem) UART. so I want minimum baud error rate. I look at https://cache.amobbs.com/bbs_upload782111/files_22/ourdev_508497.html table and decide ...
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14 views

Measure Junction capacitence of sensor

I would like to know how can I measure or calculate the junction capacitance of an oxygen sensor(or photodiode or any current source sensor). The manufacturer does not have this information on their ...
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1answer
51 views

Real world objects touching reading the same capacitance?

In my project, I am developing a capacitive sensor based system which attempts to identify if two real world objects(*) get in contact with each other. I have done my homework (some) on Capacitive ...
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499 views

What would be the combined dielectric constant of two dielectrics in series?

Let's say we have two parallel conductor plates. In the middle, there is not one but two layers of dielectrics made of different materials. If we know the relative permittivity of each dielectric, how ...
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368 views

Three phase motor driver DC link, DC bus capacitor values

I am designing a motor driver for a three phase brushless motor and have been looking for a capacitor value for the DC bus of this circuit (C1). Most of what I have found when researching deals with ...
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48 views

Sampling DC and AC components of capacitive sensor

I'm using a MEMS capacitive pressure sensor SCB10H. As I understand it, I can wire it up in one of two ways. Either I can measure the absolute capacitance using a chip like the TI FDC1004. In this ...
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320 views

Measure input capacitance of I/O pin

I'm looking for a simple laboratory procedure (and required equipment) to measure the input capacitance of each IC I/O pin. Thanks in advance.
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3answers
415 views

Capacitance Measurement With Oscilloscope

simulate this circuit – Schematic created using CircuitLab I'm trying to determine the capacitance of a sensor, but the oscilloscope's internal capacitance is loading the measurement too much. ...
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0answers
137 views

Finding the equivelent capacitance of the circuit

Finding the equivelent capacitance of: simulate this circuit – Schematic created using CircuitLab I think that it should be: $$\frac{1}{\frac{1}{C_1}+\frac{1}{C_2}}+\frac{1}{\frac{1}{C_3}+\...
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110 views

Logic gate directly driving power MOSFET

Art of Electronics, 3rd Ed, pg. 164-165 give an example of naively using a 4000-series CMOS logic gate to directly switch a power MOSFET, disregarding the significant gate current required to charge ...
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1answer
2k views

shunt capacitance the same as stray capacitance?

I need a crystal for my project and I found this crystal: https://mouser.com/ProductDetail/TXC-Corporation/9C-16000MAAJ-T?qs=sGAEpiMZZMsBj6bBr9Q9aWUu9Vmt5DeozjX1gZsyHq8%3D To calculate the two ...
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37 views

Slewed fpga drive rise time on pcb to enet phy

What can cause rise times to be slewed from an fpga to an enet Phy? Can it be trace capacitance? This is a high density 14 layer board . Traces route from fpga to ribbon connector, along a short ...
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0answers
861 views

Worst case delay for a CMOS gate

I want to determine the input pattern for the worst case tpHL of this CMOS gate. I think there may be more than one input pattern that give worst case tpHL. The following is my reasoning: The ...
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321 views

MOSFET Driving On The Cheap And Cheerful

I need (unless I'm XYing) to high side switch a FET pair from a (PIC16) microcontroller in the simplest way possible. They are switching an audio line with significant current (presently the output of ...
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83 views

What's the formula that relates capacitance, permittivity and geometric coefficient in the ring capacitor?

I find it hard to calculate the geometric coefficient of a capacitor with two cylindric electrodes and a tiny distance between them, exactly like this one : Does anybody know the exact formula? ...
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40 views

capacitance sensor between humans

I am using this module: https://www.adafruit.com/product/1374 My idea is to sense a person wearing this module and when touched by another person, the LED lights up. I read numerous articles and ...
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150 views

How to extract complex permittivity from a CV measurement?

I can choose from the following measurements: Z, theta (impedance and phase angle) R + jX (resistance and reactance) Cp-Gp (parallel capacitance and conductance) Cs-Rs (series capacitance and ...
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282 views

How to estimate ripple current for PWM loads?

I'm buying some caps for a PCB which I'm designing, and I'm not quite sure how to estimate the ripple current they need to be. This PCB is intended to switch about ~15A from 12V to 24V at ~100kHz. ...
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103 views

Charge conservation

How can I apply the theory of charge conservation for this charge pump circuit. Specifically on the pump circuit. How do I get the charges on the capacitors?
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1answer
154 views

Diffusion capacitence

I am trying to figure out the capacitance seen at each node, given that the source and drain diffusion capacitance is shared in the nmos stack. Given that the fingered layout uses a finger width of W=...
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1answer
56 views

Capacitor Units For Power Factor Correction

I have got the assignment to improve power factor of an industry. I have worked it out and found capacitance in K Vars and Micro Farads but need to know about the capacitor representation in volts?
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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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28 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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22 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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25 views

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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65 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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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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26 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
40 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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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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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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36 views

Input DCDC buck filter design equation

I am asking because I am confused. I cannot resolve this issue since yesterday and I am still learning. I was reading article about Input DC-DC buck filter. Each of the two articles say something ...
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1answer
91 views

Capacitance multiplier

In my device I'm using a "capacitance multiplier" to filter DC-DC output voltage. That's my schematic: In Multisim simulation I've achieved necessary output parameters, but when I soldered my PCB and ...
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64 views

Selecting a Capacitor for Pulsed Power

Background: I'm planning on making a hard tube modulated pulsed power supply. This will use a thyratron set to trigger at a frequency of 6 Hz, a 60 nF capacitor bank, and a 0.625 mH inductor. The ...