Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [parasitic-capacitance]

Capacitance that arises from the physical layout of the circuit and the placement of components. Particularly notable when the addition of capacitance is undesirable.

108 questions
22
votes
3 answers

Why does an inductor behave as a capacitor at high frequencies?

In truth, I've only been told this anecdotally by an instructor, but can someone explain the physics at play? I have been told that if an inductor is driven at a high enough frequency, it will begin to behave as an capacitor, but I cannot figure out…
Michael
  • 948
  • 1
  • 7
  • 23
15
votes
3 answers

Crystal oscillator load capacitance, again

There's a lot of seemingly conflicting information regarding how the load capacitance for a parallel resonant crystal is calculated. Faced with a lot of problems in recent years with non-oscillation and frequency inaccuracy, I'm asking the…
PkP
  • 7,567
  • 2
  • 23
  • 42
13
votes
1 answer

What order of magnitude should I expect the parasitic capacitance to be for a solderless breadboard?

I'm trying to account for some error in measurements for a circuit I have produced physically and simulated in spice. The only suspect seems to be the solderless breadboard as the error seems to increase with frequency.
Lightyear Buzz
  • 493
  • 2
  • 6
  • 14
9
votes
4 answers

How to calculate parasitic capacitance in a trace?

I am given the equation for parasitic-capacitance as: \$ C = \dfrac{\epsilon_r \cdot \epsilon_0 \cdot L \cdot W }{ d }\$ I am also told my trace is to be 1000 micrometers long (1mm) and 45nm wide. The spacing between traces is 45nm as well (and the…
Kapurnicus
  • 91
  • 1
  • 1
  • 2
9
votes
3 answers

Understanding capacitance in oscilloscope probe tip

I am trying to understand the capacitance and resistance in oscilloscope probe tip. In the above attached image, that 9Mohm resistance is used for that 1x and 10x setting that divides the input voltage by 10 times or not, right? But which…
user220456
8
votes
3 answers

Audio transformer: What to do with an unused winding?

For the purpose of impedance matching and floating a single-ended, ground-referenced signal, I am planning to use an audio transformer like this one. Here's the schematic from the data sheet: My source has 150 Ω and I am using an output impedance…
zebonaut
  • 18,170
  • 4
  • 60
  • 104
7
votes
2 answers

How is it possible that the reverse transfer capacitance of this FET is so low?

A FET has parasitic capacitance, which can be modeled as a capacitor between each of its terminals (gate, drain and source), which I refer to as Cgd, Cgs and Cds, as shown in the image below. FET manufacturers list other capacitances in their…
kassiopeia
  • 432
  • 1
  • 6
  • 15
6
votes
1 answer

Using only stray capacitance for MCU oscillator circuits

I've included a diagram of typical Pierce oscillator circuit taken from ST Application Note AN2867: The note suggests that C_L1 and C_L2 should be chosen such that the following equation holds: Since C_L1 and C_L2 are typically equal, this…
mablem8
  • 161
  • 1
5
votes
1 answer

Tesla coil, where do the sparks from the secondary coil ground to?

This might be an obvious question, but I was wondering how a Tesla coil emits sparks that's seem to complete a circuit in thin air, and how one end of the secondary completes a circuit with the other side of the secondary. Is this circuit simply…
user191893
  • 53
  • 2
5
votes
1 answer

Parasitic capacitor current of an inductor

I am doing a double pulse test on SiC MOSFETs from 100-800 V and current from 20-80 A. The schematic is shown below (the values are not correct though): In my first round of tests, I was getting a rather oscillatory switch current for the lower…
Autobot
  • 155
  • 1
  • 8
4
votes
2 answers

adjacent trace capacitance (horizontal)

I find a lot of online tools to calculate the capacitance between two traces (or a trace and a plane) on opposite pcb layers. One such tool can be found here: http://chemandy.com/calculators/rectangular-capacitor-calculator.htm However, I would…
K.Mulier
  • 2,327
  • 3
  • 21
  • 40
4
votes
2 answers

Header frequency limit

At what point will I start having trouble with noise and parasitic capacitance/inductance when using standard 0.1in header pins? If I'm using an MCU capable of driving a 20MHz SPI bus, would it be reasonable to run a breakout board or Arduino shield…
Caleb Reister
  • 1,301
  • 10
  • 27
4
votes
4 answers

How are MOSFET gate capacitances (Cgs, Cgd) calculated?

I have read somewhere that the gate capacitance (Cgs, Cgd) of a MOSFET is calculated as below: Strong inversion: Cgs=(2/3)Cox.W.L + Cov Non-saturated: Cgs=Cgd=(1/2)Cox.W.L + Cov where Cov is overlap capacitance. Could anyone explain where the…
emnha
  • 1,547
  • 4
  • 34
  • 84
4
votes
1 answer

Tesla coil miniature model (slayer exciter) parasitic capacitor

I have been trying this miniature Tesla coil based on Slayer's exciter circuit (shown below). The part that I don't understand is how this parasitic capacitor exists? I know that for a capacitor there needs to be 2 opposite charges separated by a…
Bhuvanesh Narayanan
  • 1,027
  • 2
  • 13
  • 23
4
votes
1 answer

MOSFET fast turn-off not enough

I have a PWM bridge driving a higher than 1k load from 200V supply. The simplified, equivalent schematic is this: The drivers I'm using are slow turn-on/fast turn-off and, in the schematic, it's a 50% duty-rati.,The parasitics modeled here also…
a concerned citizen
  • 21,167
  • 1
  • 20
  • 40
1
2 3 4 5 6 7 8