Questions tagged [impedance]

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

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Primary/Secondary Transformer Impedance, and Impedance Matching

I need to select the proper transformer to use in a device to convert from a hi-z input to a lo-z input. As far as I understand transformers have no impedance, rather a percent impedance which is ...
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Electromagnetic "floating" noise in circuit have a frequency component that affects impedance of input pin?

"The effects of capacitance and inductance vary with frequency, so if these are present the input impedance will vary with frequency. The effects of capacitance and inductance are generally most ...
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Suppose there is a standing wave in a transmission line at high power. Will the nodes of a wave 1 ft apart be hotter than the antinodes?

I was looking around for an evening and could not find an answer. I am also fuzzy on the exact electromagnetic physics principle of why a reflection occurs (please do not say "because the ...
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1answer
86 views

What does an S21 of 0dB mean?

In a video titled PDN Measurements with a VNA Rolf Ostergaard shows how to transform the magnitude of the insertion loss S21 to an impedance value. This is the formula he uses: $$ Z = 25\Omega \times ...
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What does the RZQ stands for?

While manually configuring a Memory Interface Generator in Vivado, I saw an option related to the output driver impedance. There were two options selectable, RZQ/6 ...
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Why reactance is imaginary? [duplicate]

In AC circuit, cartesian impedance formula is Z = R + jX (Z = impedance, R = resistance, X = reactance). Why is reactance imaginary (for capacitors and inductors)? I cannot find a good explanation ...
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Transmission line and input impedance - Smith chart

According to "Smith Chart Supplement - Corrected Jan 2012" https://www.arrl.org/files/file/Antenna%20Book%20Supplemental%20Files/22nd%20Edition/Smith%20Chart%20Supplement%20-%20Corrected%...
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How to use two power sources in a DC circuit

If you haven't read the original post, you can skip to the 2021/09/09 5P PST update Shortly after starting to work with basic circuits (not too long ago), I was convinced that all electricity within a ...
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Converting 4-20mA to 0-5V to 3.3V

I have a pressure transmitter that I supply 12VDC to which outputs a 4-20mA signal. The circuit is based on an example in the datasheet (figure1, page5). The problem is I now need to take this ...
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Impedance of loop wire

I need to calculate the total impedance of a 3 mm diameter wire loop of 320 µm magnet wire with 5 mm of feed length at 3 GHz. My approach is: $$ \newcommand{\subs}[1]{Z_{\text{#1}}} \newcommand{\Z}[1]{...
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How to interpret VNA data?

I'm looking at the raw data from a VNA (HP 8720A) and I want to understand how to interpret it, and how to do after-the-fact calibration (ie: read raw data, then apply to it whatever corrections a ...
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2answers
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How do I find the magnitude of a complicated complex number? [closed]

How do I find the magnitude of something like $$1+(Z_c+R) \times Z_l$$? (\$Z_l\$ is the impedance of an inductor.)
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1answer
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Impedance Divider Network

Need help with this impedance divider network. I was going to evaluate it like I would resistances but I'm not sure if that's correct. I'm thinking Zc1 has no effect on Vout so it can be ignored and I ...
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Trace impedance ohm meaning

I've been trying to understand the principle of trace impedance (single ended and differential) for a while, read several articles (all the best google has to offer), but I have still some serious ...
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1answer
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What kind of inductor to choose?

Which kind of inductor should I choose if value is the same? rolled over a ferrite rolled over a plastic rolled in air rolled in a package looking like a resistor Is it related to specific roles? ...
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1answer
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How to calculate the Vout/Vin in this circuit? And how to write this circuit in a simulator like PSPICE? (buffer)

This question is about this circuit, a signal conditioning circuit. I am trying to the discover the Vout/Vin, I think it is one but I can't demonstrate it. I can't figure out why these resistors and ...
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Impedance, amplitude and Thevenin equivalent

I have an exercise of medical electronics to complete and I am confused by the question, I've looked through material and classes and can't find examples of impedance and amplitude of thevenin ...
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1answer
99 views

Does the self inductance and velocity factor of the elements of a dipole antenna change its resonant frequency?

Below are well known equations from Wikipedia for the resistance and reactance in the impedance of a dipole antenna. where a is the radius of the conductors, k is the wave number 2πf/c, η0 denotes ...
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2answers
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I need help with a microphone issue for my aviation headset [closed]

This is my first time asking for help in a forum so I hope I can do it properly. My problem is this: I have an aviation headset with a non working microphone and I would like to try make a microphone ...
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2answers
55 views

Conductance and resistance of an acoustic transducer

I have the conductance and susceptance vs. grequency data on an acoustic transducer. Also mentioned is the resonant resistance and resonant capacitance which is just the inverse of the conductance and ...
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41 views

Voltage drop calculation

The impedance of a single phase load with a supply voltage of 120 Volts AC is 2.80+j2.076Ω. The load draws 30 amps at 85% lagging power factor. Determine the size of the conductor used to supply power ...
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1answer
57 views

Impedance to supply voltage

Looking at this question in a design exercise. I'm trying to work out where the impedance to the 9V power supply comes from. It's given the typical complex impedance of a PCB track at 1kHz is 0.1 + j0....
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63 views

Impedance of PCB track

I was wondering if PCB tracks have a typical complex impedance? This is for a signal of frequency 1khz.
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188 views

Why is there no reactance in the impedance of a half wave dipole antenna?

For a resonant 1/2 wave dipole when used for transmitting, does the fact that the reflected waves on the antenna are in phase with the applied signal result in zero reactance at the feed point, or ...
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1answer
43 views

Problems with track for LoRa RF

Following up on this question, I am using an RN2903 module with a U.FL connector (with an additional option for a through-hole wire antenna). My PCB looks like this: I used this coplanar waveguide ...
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1answer
66 views

Is the increase of impedance over a small hatch area on a FlexPCB negligible?

I have a FlexPCB with 4 layers and total thickness of about 200 µm. The second layer is a ground plane that is solid copper over the entire FlexPCB. To increase flexibility of the FlexPCB, I want to ...
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2answers
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How do I calculate sound pressure level (dB SPL) from headphones at a specific setting on my sound card?

I am using headphones with sensitivity 102 dB SPL / 1 Vrms with impedance of 300 ohms. For a particular volume knob setting on my sound card embedded with a headphone pre-amplifier, I would like to ...
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1answer
78 views

How to choose the right value for a emitter cap for an RC oscillator?

I have a circuit like this: Given a low or a high impedance feedback network, how do I choose the right emitter cap value Ce? I know that the emitter cap depends on the impedance of the feedback ...
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How would you design a power divider with 50-Ohm unbalanced input and 4x 100-Ohm balanced output impedances to send RF down a CAT6 cable?

A CAT6 cable has 4 balanced pairs, each at 100 Ohm. I'm wondering if I can make a 50-Ohm coax unbalanced input and split the power to 4x 100-Ohm balanced output (and then merge it back together the ...
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1answer
48 views

Impedance sensing technology with headphone extension cord [closed]

I have a simple question and I've tried researching the topic but I don't understand the technology. My computer uses impedance sensing technology to set the impedance for headphones. My situation is ...
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3answers
103 views

matching impedance transformer in old designs

I want you to see my question from an "historical point of view"... Building circuits that I found in magazines of the '60 I see a lot of interstage transformer between Ge transistor stages ...
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1answer
121 views

Doubt about 50 ohm impedance calculation

I am developing a 4-layer FR-4 board containing a GNSS receiver (L1 + L2). RF tracks must have an impedance of 50 ohms. The board contains two inner layers of GND and a ground plane around the RF ...
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Two transmission lines with different media

I have some questions about intrinsic impedance and characteristic impedance. I learned the reflection of a wave occurs if the intrinsic impedance of the materials is different. \$ \Gamma = \frac{\...
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Equivalent impedance through a transistor

I'm looking for the equation of the equivalent impedance through the network. This is all the information I was given, other than that the transistor is biased in the saturation region and rds isn't ...
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2answers
108 views

Why is an infinite reactance an open circuit?

I'm writing up a summary about classic impedances (resistors \$Z_R=R\$, capacitors \$Z_C=1/j\omega C\$ and inductors \$Z_L = j\omega L\$) for students starting out with AC networks. I was about to ...
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Coupling coefficient in function of reactance

If there are two coupled inductances L1 and L2, we may want to write k in function of the reactances, that is, in function of Z_L1 and Z_L2. How would you do so?
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Impedance value effect on voltage measurement

When I measure voltage of, for instance, the open circuit voltage at low luminous intensity of a photodetector with ADC Adruino Uno an offset appears. The value is good if the photodecteor (here an ...
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1answer
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Resistance of JFET when used as a voltage controlled resistor

We have designed a circuit for a bidirectional current limiter using an N-channel JFET as below: This limiter is connected to the end of electrode used for EEG measurement. The requirement for the ...
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2answers
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Transmission Line Step Response

This question seeks a canonical answer to a question regarding the transient response of a transmission line. Suppose one has a transmission line, long enough to be considered "infinite" for ...
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Meaning of "impedance looking into..."?

I know that this is a very basic question. While learning electronics, I see the phrase "the impedance looking into X" very often (e.g. in The Art of Electronics, 3rd edition), but I haven't ...
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1answer
59 views

Are impedance calculations only specific to sinusoidal inputs?

All impedance formulae we've derived in my course and calculations e.g. combined impedances in series have all assumed sinusoidal steady state. My question is, does the notion of "impedance" ...
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2answers
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Frequency-dependent behavior of a resistor in time domain simulation

I know for a fact that to take into account frequency-dependent behavior in time domain simulation, equivalent electrical networks that reproduce the same frequency behavior are used, as it happens, ...
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2answers
59 views

Basic RL curcuit problem

So I had an exam in basic electronics, which I passed but lost a lot of points on one seemingly easy task. "Through the coil is passing a current equal to \$i_L=200\sin(10^5 t + 210°)\$. If R=5 ...
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5answers
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how to calculate and express equivalent looking into two nodes in helpful combinations?

I'm trying to find the resistance \$Z_{CE}\$ looking into C, E terminals of the circuit below when \$V_{IN} = 0\$. I introduced ...
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2answers
51 views

Thevenin equivalent of open ended transmission line Clarifications required

I am going through the below link for understanding about transmission line reflections. The below figure is an equivalent circuit of an open-ended transmission line. For finding the the voltage at V+ ...
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2answers
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What does mean if there is P+ and Q-?

If in a circuit there is real power positive and reactive power negative, what does mean in terms of power flow? I undestand that the real power is produced in the generator/source and goes to the ...
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Difference between USB Single ended impedance and common mode impedance

I was learning about USB2.0 layout guidelines from this material[USB Layout Guidelines]. In page no 2 you can see the statement that says a single ended impedance is not critical as differential ...
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1answer
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Sequence Impedance/Zero Sequence Impedance of lines

I am trying to calculate the Sequence Impedance/Zero Sequence Impedance of couple of lines, but Im not sure if the calculation are right, and besides there are some tricky things on the data provided. ...
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171 views

WS2812B first LED flickering Wemos D1 mini

I'm running 110 WS2812B LEDs with an Wemos D1 mini clone (AZDelivery) and the first LED flickers and won't even turn off but rather show red or green. I changed the data line cable several times, ...
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1answer
103 views

Trace impedance calculation in Altium for RF

I am routing the RF trace for a Microchip RN2903 LoRa module. The datasheet states the following: I wanted to use Altium to calculate the width of the trace automatically, so that it had a 50 Ohm ...

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