Questions tagged [impedance]

Impedance defines the voltage/current characteristic of any dipole circuit.

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Impedance in sine DC

If we have a DC sine signal. Can we say that capacitors and inductors have impedance despite not being AC? If yes then what will the formula look like? And the opposite if we have an AC square signal ...
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Emulate impedance response using RLC components

I need to emulate measured impedance response of some blackbox using only RLC components. Measurements: ...
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68 views

How to choose speaker impedance for a VERY specific application?

Ok, so this may be a long post. I want to preface by saying I have very limited electrical engineering knowledge, so thank you in advance :-) I'm working on a medical device for a college project. ...
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Electrical circuits homework

I am pretty new to circuits analysis and I have the following problem as homework: ig2(t) = 4sin(ωt + π/4), e3(t) = 12sin(ωt + π/4), R1 = 10 Ω, ωL1 = 4 Ω, ωL3 = 3 Ω, 1/(ωC2) = 6 Ω I have to calculate ...
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75 Ohm Coaxial Cable Used On a 600 Ohm Output

I'm working on restoring an HP 211A square-wave generator and I'm looking to add a shielded cable to the 600 ohm output. I've got some spare 75 ohm RG59 cabling and I was wanting to know if using that ...
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48 views

Why is 370HR used for controlled impedance rather than FR4?

I tried to put together a quote for a 4-layer PCB with controlled impedance (Displayport, so 100ohm differential +/- 10%). I used the online quote tool on Advanced Circuits (4pcb.com). The quote ...
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33 views

Finding the total impedance and voltage across open terminals

The question that I'm trying to solve is the following: In the circuit shown below, what is the total impedance in ohms across the open terminals? What is \$v_{T}\$ if \$v_{L}\$ is 80 vrms? This is ...
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Measuring Output Impedance of an RF (HF/VHF) Active Circuit with Hobby-level Tools [migrated]

Is there a simple (by simple, I mean a hobby friendly method that trades some accuracy for expense) method of measuring the "actual" output impedance of an active or "hot" RF (HF ...
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Parallel trace signal integrity: Increasing width to match characteristic impedance vs increasing trace gap

Imagine you are routing a large number of single ended high speed traces through a long narrow gap on a PCB. Lets say these are ultra-high speed SD signals, so a 208MHz clock. The traces should be ...
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58 views

How to connect a low impedance RF amplifier to an antenna?

I'm trying to maximize power transfer from my amplifier to my custom antenna, but am unsure about how to properly impedance match the system. My amplifier has an output impedance of 4Ω, but is ...
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Realisation conditions for impedances

Given a frequency function, which conditions should it fulfill to be realisable and implemented as a one-port impedance? I know that for it to be realisable with passive RLC components, the frequency ...
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82 views

Help with output impedance of a circuit

We have to find the output impedance of the following circuit, where the output is the upper pin of R4. If I try to compute it with LTspice, I get about 55 Ohm, but whenever I try to work on it ...
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Measuring the impedance of dry EEG electrodes?

Does anyone have recommendations or good resources on measuring the impedance of active dry EEG electrodes? I'm working on a project to create my own electrodes, and I'm pretty new to the electronics ...
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Equivalent impedance seen at input terminals of inverter stage

I am using a three phase interleaved DC-DC boost converter which is followed by the three phase inverter. I need to model the impedance seen by the DC-DC converter when inverter load is connected to ...
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1answer
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Am I using the right resistors with these MOSFETs for an ESP8266 controlled LED strip?

this is my first question here. I hope I don't mess it up. I made a WiFi controlled LED strip about a year ago. The LED strip is one of the "dumb" (no individual pixel control) 12V ones and I used a ...
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What does a High Impedance input mean for an ADC

The ADC ADS131M08 list a feature: Can someone elaborate what this feature implies? Does this mean i can place a 300 Kohm resistor in series with the inputs? There is even a reference on page 88 with ...
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ST ST25R95 - NFC chip - Impedance of transmission lines

I will supply the chip with 3.3V, and the datasheet of ST25R95 IC shows it has a ZOUT of 27R at this condition. There is a circuit between NFC antenna/coil/inductor and the IC, the LC filter and ...
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Why adding capacitor to a 10x passive oscilloscope probe

I'm trying to understanding input impedance and its circuitry of a simple, passive oscilloscope 10x probe. From reading Input Impedance of an Oscilloscope and the video EEVblog #453 - Mysteries of x1 ...
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Piezoelectric Backscatter Communication

I am currently working on a project. We have a metal bar as test object and at each end we stuck a piezo disc. I am trying to use one piezo as a sender and the other as receiver or reflector. I tried ...
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54 views

Formula derivation of Doherty power amplifier from circuit diagram

I'm having a hard time understanding how formulas are derived from the diagram of a simple Doherty power amplifier circuit, as pictured below. While I understand the concept behind load modulation ...
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1answer
34 views

Impedance Matching of an Antenna

I am reading about antenna design and have a few questions which I could not get clarified. I read about "Stubs". I got to know that Stubs are used for impedance matching of an Antenna either by ...
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Two port networks - Why are shared Z-parameters not negative?

In basic electronics we learned that to solve a circuit using mesh analysis, the shared impedances had to be negative. For example in the circuit bellow, the system of equations would be: $$\begin{...
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3answers
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What is the best way to measure current and voltage through a diode

I am reading the book Learning the art of electronics and on a part about diodes, the author pointed out that in characterizing a diode(I, V relation ) there is an unavoidable error due to the ammeter ...
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relation between transmission line & circuit impedance

What is the relation between the impedance of lumped components and the characteristic impedance of transmission lines? I have noticed that in some cases transmission lines are loaded with lumped ...
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2answers
51 views

How does Impedance matching equation work out from original link?

From this link: L-Pad Impedance Matching Equation How do you get those two equations? They do not look like a voltage divider formula, do they? Questions repeated here: First answer from Adil ...
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Should I cut away the ground pour above a diffpair on the first inner layer, which are Z-matched to the ground layer (L2)?

I'm routing diffpairs on the 1st inner layer of a 4-layer pcb which are Z-matched to the 2nd inner layer which is entirely a ground pour. The top layer has traces and routing AND also a ground pour ...
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Is my thinking right for the simple harmonic circuit

If this is a simple harmonic circuit, then what is the \$X_C\$? I know harmonic circuit means that there is no value in the imaginary part of the impendence or admittance, that is, \$Z_{th}=R+0j\$ or ...
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Impedance and resonance frequency of a bias tee

I am a beginner trying to learn about combining impedances and solving for the resonance frequency. I am solving a circuit: simulate this circuit – Schematic created using CircuitLab and I ...
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76 views

Speaker impedance and voltage

There is a device which has output impedance 150ohms. If my headphone has either lower(30ohms) or higher (400ohms) impedance can I use it or sound will be too low/high and it will be unsable? Also, ...
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51 views

Deriving the Impedance equation of a RLC circuit (with 2 Inductor)

simulate this circuit – Schematic created using CircuitLab During this lockdown I had some time in hand and decided to learn more about impedance. So I gave myself a project, trying to create a ...
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Advice for 90 Ohm traces of a USB 2.0 HUB

I am designing a USB-hub that has many USB traces. I followed some guidelines online and read forums. Based on my understanding of a 4-layer stack-up, one of the best set-up I chose is 8 mil trace ...
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What is impeding current when voltage is stepped up in a transformer? [duplicate]

What is physically impeding electric current when a transformer steps up voltage? Is there some EM field along the conductor impeding electron movement? FYI, I'm not asking about losses or leakage. (...
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Cadence - input impedance

What is the best way to find the input impedance of an amplifier using cadence software? is it by using the smith chart or is there an easier way? do I have to add an additional components to the ...
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1answer
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How to calculate the PI model equivalent transformer parameters

I have a power transformer with the transformer ratio 200kV/100kV, 100MVA rated power, and specified R = 0.001 p.u., X = 0.05 p.u. For a calculation I have to make, the literature I am using is ...
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47 views

Typical impedance values for a large 150 MVA power transformer

I am trying to calculate the impedance in ohms for a 220kV/110kV 150MVA transformer (European grid), but the values I am getting are not in range of values I usually see in online examples. X in p.u....
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Can you reduce audio noise by decreasing input impedance with a resistive load?

First asked this over at sound stackexchange but they pointed me over here as a better place for it. A general question but inspired by a specific example so framed as such. I have powered studio ...
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Simplifying expression for total impedance of an equivalent circuit in EIS

In electrochemical impedance spectroscopy applied to impedance response of an electrode, when charge transfer resistance \$R_{ct}\$ and Warburg impedance \$W\$ are in series in an equivalent circuit, ...
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Input impedance for a darlington pair

I want to calculate the input impedance when I am using a Darlington pair and I'm getting a little confused on the appropriate equation to use. In Electronic Devices by Floyd he gives and example of ...
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Transmission Bus Admittance Question

I have a question about calculating the admittance between buses in the single line diagram shown below: The solution I have been given shows that the admittance between bus 2-2 is found by adding ...
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4answers
333 views

Calculate output impedance of emitter follower

In AoE's chapter on BJT (specifically section 2.2.3B Input and Output Impedances of Emitter followers), it derives the input and output impedances to be: $$\mathbf{Z}_{in} = (\beta+1)\mathbf{Z}_{load}...
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Oscilloscope voltage readings factor of 10 too high. Is this due to the impedance?

For a university physics experiment, I built a circuit to test voltage (and conductance) steps across a nanowire break junction. The break junction was in a circuit with an I-V converter, and the I-V ...
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Engineering very high impedance resonator with coplanar waveguides

I have very little knowledge of electrical engineering, so please understand if my questions are somewhat trivial. I have read that a coplanar waveguide (CPWG) acts as a lumped LC oscillator circuit, ...
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why is the the Line voltage drop formula is \$\Delta V=2I_1 (Rcos\theta+Xsin\theta)\$,not \$\Delta V=2I_1(\sqrt{R^2+X^2})\$?

There is a single-phase two-wire system,if the resistor \$(R)\$ of line is 1Ω and the reactance \$(X)\$ of line is 2Ω,and the power factor is \$\theta\$ .The Line voltage drop formula should be $$\...
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68 views

The explanation about why do we define the formula of Characteristic impedance,propagation constant and Velocity propagation

There is a long transmission line 1.Characteristic impedance \$Z_C=\sqrt{\frac{z}{y}}=\sqrt{\frac{impedance}{admittance}}\$,and in the lossless line,\$Z_C=\sqrt{\frac{L}{C}}\$ 2.propagation ...
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why can i only know conductance and susceptance,not impedance from open-circuit test?

1.open-circuit test determine the electrical conductance and susceptance,not impedance 2.close-circuit test determine the impedance ,not electrical conductance and susceptance First,i want to ask ...
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Low-pass filter - choosing R values dependent on the load impedance

I need to design a low-pass RC filter that is connected to an oscilloscope at the output. The oscilloscope has a load impedance of 1MΩ||20pF. I have to choose values for R and C, taking this load ...
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Input/output impedance of devices in a circuit simulator

I have to use a circuit simulator (I'm using Proteus, but can also use Multisim if necessary), to construct and analyse a passive RC filter. The general circuit is shown below: I need to connect ...
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1answer
49 views

Questions regarding AFG3000C function generator

I have a new function generator - model AFG3000C. I am having difficulty in understanding certain terms related to this function generator. I have tried online searches, but I couldn't get what I ...
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What is a first order, second order, third order degeneration impedance in the context of CTLE?

Perhaps I am not using the correct terminology. I am trying to figure out what differentiates first order, second order .... impedance.
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What is the peak of the short circuit current

I have this problem: Consider the circuit below: \$V_{in}\$ has an amplitude of 17V and a frequency of 125 kHz. What is the peak of the short circuit current between the terminals \$a\$ and \$b\$? ...

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