Questions tagged [capacitance]

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

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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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64 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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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
74 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
46 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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66 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
2k views

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
53 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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2answers
93 views

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
39 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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1answer
44 views

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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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
36 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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20 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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4answers
118 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
80 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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49 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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2answers
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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
41 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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2answers
49 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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25 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
36 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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2answers
65 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
37 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
77 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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2answers
84 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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1answer
75 views

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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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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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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1answer
30 views

In what situation,we should consider the balanced bridge when we calculate the equivalent capacity?

Question: Find the value of the equivalent capacitance between \$a\$ and \$b\$ Solution:Because of the balanced bridge,so the circuit become So \$C_{ab}=30 \mu //[(4\mu // 6\mu)+((6\mu // 9\mu))]=5\...
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2answers
72 views

High Voltage and Low Charge - Analogy (ESD & Lightning)

How can something have high voltage but low charge? Can anyone provide an analogy for this? I was going through the ESD topics and read the ESD events usually have high voltage but have low charge? ...
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1answer
44 views

How to calculate a capacitance of a probe in a equivalent circuit of oscilloscope?

I want to caculate the value of capacitance of probe which makes the transfer function H(s) from V_in to V_out become equal to 1/10 at all frequencies. How can I calculate it? Thanks in advance :)
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1answer
62 views

How to take Time Measurements using LT Spice

I've been fooling around with LT spice .MEAS feature for a while now and I just can't seem to determine how to take the time measurements I need for an assignment. I can look at the time values on ...
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5answers
175 views

What is input capacitance of pins in IC and what effect does it have?

What is the purpose and the definition of the input capacitance parameter in the datasheet. I have tried to research about this topic but was only able to find the input capacitance parameter with ...
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0answers
35 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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0answers
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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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1answer
81 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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1answer
27 views

How to properly calculate current of a variable capacitor?

So the formula i(t)=CdV/dt works for a constant value of a capacitor, but in a variable capacitor, i found the next formula on another site i(t)=C(t)*dV(t)/dt + V(t)*dC(t)/dt Is this formula ...
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1answer
49 views

Drop-out voltage at the input using MOSFET

Please have a look at my below circuits. The first one is an MOSFET. N-MOS. Gate is fed with a function generator input of 5V peak to peak. 1kHz frequency. 1ms period. 90% duty cycle. Drain is ...
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1answer
51 views

Capacitor Voltage Hold up (During Input Power Interruption)

I want to understand how long a capacitor can provide the stable voltage for a given load current, in the event of an input voltage interruption? Suppose, I have a single 100nF input capacitor at my ...
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46 views

Can a Varistor be used as a Capacitor?

Let's say to protect a line (DC, signal or power), I place a varistor between the line and GND. Basically to avoid large surge of current. Then, it happens, that on the same line, I also need a 1000pF ...
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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 ...
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3answers
81 views

Replace ONE 25v 47uf capacitor with FIVE 60v 10uf capacitors parallel?

MY 1000 Watt True Sine Power Inverter blew a 25V 47uf capacitor. The shell was rattling around inside, and the ribbons were exposed. Yay, I found the problem! Sooooo, how can I tell the mounting ...
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1answer
47 views

How can I find the capacitance value changes that will result in linear tuning steps in a parallel LC circuit?

I've found articles that derive the shape of a mechanical capacitor plate so as to achieve linear frequency tuning for linear dial rotation as in each degree of rotation shifts the frequency the same ...
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1answer
21 views

Difference between IRMS and Peak Current on Capacitor Rating

Background: I was looking at a spec sheet for a round metallized polypropylene film capacitor that gave two different current values for the "IRMS at 100 kHz -70 deg C" and the "Peak Current" I'm ...
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1answer
60 views

What material should I use for the plates of my homemade mica capacitors?

I recently acquired some mica as i want to build my own high voltage (50 kV if possible) capacitors. The problem I am encountering right now is that the surface of such a crystal isn't perfectly flat ...
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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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