Questions tagged [impedance]
Impedance defines the voltage/current characteristic of any dipole circuit.
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Antenna input impedance calculation
I am attempting to calculate an antenna's input impedance. I have been given this information:
A 50 Ω coaxial line is feeding the antenna a 150 MHz frequency. It has a dielectric constant of 2.25, ...
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Capacitance between parallel plates [closed]
I am designing a parallel plate capacitor for measuring the void fraction in a tube. I am using two electrodes that surround the tube and the dielectric material is a combination of water and air. My ...
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Complex number or absolute number for impedance
I am reading about high speed PCB layout design from TI (Texas pdf)
This document mentioned the software AppCAD from Agilent to calculate impedance. Here is the snapshot.
My question here is whether ...
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Controlled impedance stackup questions
In this stackup (I know that it is not the best stackup but it is a general question,) if I choose to use controlled impedance on L4 (let's say 50 ohm), what is the ...
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What is the difference between these two input impedance equations?
I'm currently solving some university E&M homework problems and to solve input impedance, we were given this formula (from Fundamentals of Applied Electromagnetics 6th Ed):
But when I browse ...
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Negative resistance circuit stability
Assume we have this circuit:
simulate this circuit – Schematic created using CircuitLab
Which will be the current flowing in such a circuit.Can we say that the resistors are in resonance?(...
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Complex voltage and current
Someone can explain me the phenomena in rlc circuit. If we have an input voltage \$V_e = V_{max}\sin(wt)\$. Why the current resulting when it is written in books is not a complex number? And why the ...
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RF design_output impedance of the SX1280 LoRa transceiver
I searched the datasheet of the Semtech SX1280, but I can't find the output impedance of the SX1280 (RFIO's pin). Where can I find it?
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Impedance matching 133 MHz - Topology and terminating resistor concerns
I am using the QSPI bus of the RP2040 to talk to a flash chip. I am also putting 8 more chips (PSRAMs) on that bus in my design, and a second RP2040 to load them. The datasheet for the RP2040 isn't ...
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AC - impedance for a coaxial cable
Problem
I want to calculate the AC impedance for a coaxial cable. A rough image is presented below:
Because we have an AC current, suppose that the skin depth, which we can define as \$\delta\$ is ...
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Ferrite bead or inductor
I'm using this device VSC8514 and this is its checklist.
I just want to know what spec of ferrite bead I should use for this device's power rails.
They have neither mentioned this in the checklist nor ...
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What is blocking impedance (specifically in a substation)
Can someone please explain what blocking impedance means when it comes to discussion of wave traps in a substation. I always see the blocking impedance listed as either 1000 ohms blocking or 400 ohms ...
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UHF RFID antenna
When designing a UHF RFID antenna, besides matching to the chip, is there some matching to air that needs to be done (for example, to the characteristic 377 Ω)?
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Relative short-circuit impedance of a three-phase transformer
I am trying to calculate the (absolute) short-circuit impedance from the relative short-circuit impedance of a three-phase transformer. I am not sure if my formula is correct, especially concerning \$\...
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Crystal resonator characterization in frequency and time domain
I want to measure a 32.768 kHz crystal resonator (not oscillator) in the frequency and the time domain using a ZURICH HF2LI instrument, which is a network analyzer and oscilloscope in one unit.
The ...
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Output impedance of the circuit
I would like to know what the output impedance of this circuit is (the impedance seen by the node output).
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Frequency response of LC filter with resistance in parallel with the capacitor
The following is the diagram of interest:
The impedance of the filter is:
$$Z_o=\frac{R_f L_f s}{R_f L_f C_f s^2+L_f s+R_f}$$
and the bode plot with all different components and the total impedance ...
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Input impedance of an electronic load
I would like to simulate a TVS with an electronic load working in constant voltage. I could add some resistor in serie with the electronic load to simulate the dynamic resistor of the TVS. ...
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Impedance Measurement Point
I've been doing some work with interstage impedance and I keep getting confused and I can't seem to get the correct answer myself. I know Input Impedance should be 10x the amount of the previous ...
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Finding the value of supply voltage in this RLC circuit
We need to find the value of V, Power Factor, and Power Absorbed in the circuit.
I am stuck at resolving the two parallel branches.
I started out by labeling the impedances of the three given ...
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Circuit simplification to find Thévenin resistance
I've been trying to work out an equivalent resistance using Thévenin, but I'm not 100% sure if what I've done is correct or if I'm missing steps. I've attached my "working out" (this isn't a ...
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Source impedance influence on DC/DC converter input impedance measurement
simulate this circuit – Schematic created using CircuitLab
I have been tasked to verify the input impedance of a medium powered DC/DC converter (<1kW), and no experienced colleagues to ...
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Why do cables specify 75 Ω impedance when impedance is a two-dimensional quantity?
As I understand it, impedance has an imaginary and a real part. To be able to perform any useful calculations, one needs to know both. Cables and speakers usually only say like "8 Ω" or &...
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What is the difference between Smith charts plotting Z11 and S11?
Background
In the process of trying to fix an LNA input impedance match, we discovered we need to understand more about Smith charts! The question is the at the bottom of this post, here's some ...
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Drive strength and impedance
I have a custom embedded board with an MPU (i.MX6ULL) interfaced to a DDR3L. After noticing occasional hangs and crashes, I started tinkering with the DDR Drive Strength settings and was surprised how ...
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Why doesn't the real part of the impedance always equal to the resistor in an ideal parallel RC circuit?
A little confused when doing a quite simple AC simulation in ADS with a parallel RC circuit.
2 kΩ in parallel with a 12 pF. See the picture:
My question is that why the real part of the impedance ...
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Calculating harmonic currents of a circuit with L and R
I want to calculate harmonic currents of the following circuit in LTSpice. Circuit operates with 100MHz square wave with 1ns rising and 1ns falling edge and 5V:
In FFT view, LTSPice shows me that ...
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Question regarding IBIS models
I have the IBIS models for this SY75603 PCIe clock buffer IC.
However, the available IBIS model is only for the SY75603A with 85 Ω outputs; I'm using the SY75603B with 100 Ω outputs.
What should I do ...
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How can I calculate RC circuit impedance and phase difference in parallel?
Most of articles on the web, define capacitor as ideal capacitor. I want calculate impedance and phase difference of this circuit with capacitor ESR.
For example :
simulate this circuit – ...
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Algorithm for impedance calculation from known I and V sinusoids, L and C unknown
I am trying to extract the impedance from a sampled signal. Specifically, I have only noisy samples of a sinusoid, of a single period, of current and voltage at a given known frequency. I am trying to ...
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How was the highlighted value obtained?
I'm currently calculating the excitation current for a transformer but I keep getting the wrong answer. I tried converting the highlighted values to rectangular form (first highlighted value) but ...
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Audio line-out to amplifier line-in matching impedance and voltage
I am an electronics hobbyist. After reading online my understanding is that an op-amp buffer or JFET pre-amp can be used to match a medium (lower) input impedance with a high output impedance. In my ...
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What does the "impedance" value of audio transformers specifically mean in terms of inductance?
So I've searched the web, looked into other questions here (e.g. this one), but I am not really any wiser.
What does the impedance of a transformer specifically mean? I.e. how can I deduce the ...
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Calculating impedance by amplitude and phase angle
I want to determine the resistance \$R_k\$ and capacitance \$C_k\$ of this simple RC network by measuring the total and the shunt voltage:
simulate this circuit – Schematic created using ...
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Trace impedance with different ground reference planes
I have a PCB board stackup that includes ground pour layers adjacent to a controlled-impedance signal layer. However, the ground planes are not the same reference plane - one is an analog ground plane ...
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How can I calculate the total impedance of a second-order low-pass filter?
How can I calculate total impedance of this low-pass filter? Also, how can I measure the phase difference?
For example:
L = 12.73 mH
C = 198 μF
R = 8 Ω
F = 100 Hz
Simulators show a graph as top:
...
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Speaker impedance & wattage [closed]
I have a 15 W + 15 W amplifier per channel, it will give 15 W at 4 ohm and 10 W at 8 ohm. My speakers are 4 ohm, 10 watts. Do I add 4.7 ohm 5 W wirewound resistors in series with each speaker? Will ...
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Impedance matching
I am a newbie at microwave. I'm confused about impedance matching. So far just 50 Ω impedance stub in outside.
But in this example below I saw 75 Ω. I could use the Smith Chart but I didn't know how ...
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RF - How to layout component pads that are not the same size as the coplanar waveguide track width
I'm currently rough drafting a RF/microwave pcb which I hope will be fairly wideband, from Mhz to possibly 6-7GHz. (not sure if it's possible). Anyway, when laying out the various components I find ...
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Input impedance when an opto-isolator is in series
My circuit is detecting 24Vac/dc signals with an opto isolator at the input. HCPL354 is the opto isolator and I am adding 4.4Kohms resistance in series to limit the current. When I make the datasheet ...
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How does filling a via with solder change its resistance or impedance?
For instance, let's assume a copper trace width of 10 mm on both sides of a double-layer FR4 board with a thickness of 1.5 mm, copper thickness 35 µm (1 ounce per square foot).
The traces are ...
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Are there measured values for the resistance contribution of vias of different diameters and depths?
I'm interested to know if there are real-world measurement values available for the resistance contribution of vias (or plated through holes).
Sure - there is no widespread definition of what a ...
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Do 50 Ω signal generators have a series resistor or not?
I am wondering about something really simple and silly.
If functions generators have an internal series 50 Ω termination, then they would produce only half the set amplitude over a matched load.
...
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Step-Up Transformer parameters
Currently I am tinkering on a project including a high-voltage output.
My current design is:
Use a power-op amp (OPA547 Datasheet ) with +-24V-Rails at x4 non-inverting gain and feed it with a +-5V ...
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Measuring variable impedance
I was wondering how to design a measurement system that's able to correctly measure a load impedance that can vary over time and can possibly have very low as well as very high values (see figure ...
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How does a voltage divider work?
I have a simple question regarding the voltage divider.
Let's say we have the case as in the image below:
I know the formula for the division of voltage at \$V_{out}\$.
My question is what happens if ...
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Inductor impedance
I feel like I'm missing/forgotten something fundamental with regards to impedances.
For an inductor \$X_L=2πfL\$, so for a 68uH at 500kHz \$X_L = 2π \times 500\text{ k} \times 68\text{ u} = 214Ω\$.
So ...
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Criticism / Advice on 5th order bandpass filter evaluation board
I 'designed' a PCB for a 5th order bandpass with SMA pcb edge mount connectors.
I've calculated the impedance to match 50 Ohm as a coplanar waveguide.
The track specification is width = 1.27mm and 0....
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What effect does termination impedance have on propagation speed?
I fed a 1 MHz sinewave from a 50 ohm signal generator source into a 100 ft long RG58C coax cable "T"ed into a 100 MHz dual trace scope channel 1. The other end of the cable was fed into ...
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What does the double vertical bar mean here?
I'm reading on air "gap impedance" and came across this equation from these notes on the topic. http://web.mit.edu/6.685/www/chapter8.pdf (see page 7).
The article defines this equation as: ...
