Questions tagged [impedance]
Impedance defines the voltage/current characteristic of any dipole circuit.
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How to build a 75 ohm to 50 ohm converter [closed]
I need help to build a simple converter to match a 75 ohm feed line to a 50 ohm antenna. Please help :-(
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Impedance matching confusion
A long time ago I understood this, but right now it totally escapes me.
Taking an audio amplifier for example. Say it drives a speaker which is 8 ohms at all frequencies. Taking the amplifier as a ...
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Q factor for an LRC series circuit
Trying to prove to myself that the Q factor for an LRC series circuit is \$\sqrt{L/C}/R\$, but I am struggling with it...
My reasoning runs that the half power upper frequency limit is (ignoring the \...
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Decrease Impedance at Higher Frequencies
I am trying to see if I understand how impedance works correctly before I build this into a real circuit. Basically I have an inductor (helmholtz coil) driven by a function generator, now by itself we ...
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FEM: How to calculate impedance in stator circuit for loaded generator
I am modeling a synchronous generator and in the stator circuit consisting of 3 phases at the alternator output, I have resistances and inductances of the end windings. Thus I have a 3D approximation ...
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Can the characteristic impedance Z0 of a conductor be measured?
We have a custom made data cable at my work, is there any good way to measure \$Z_0\$ of a cable, or must the formulas be used?
Trying to work out what value termination resistor to use.
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Op-amp input resistor?
I'm reading through the datasheet for the TL064, which contains this figure on page 16:
This is an instrumentation amplifier that apparently uses an inverting amplifier's output instead of a ground ...
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Maximum Power Transfer in an AC Circuit
Consider an AC voltage source is placed in series with a complex impedance (z) and a load impedance. The maximum power transfer to the load impedance occurs when the load impedance equals the complex ...
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How to compute input impedance?
I use a Sallen-Key filter for a project at university and I need to know its input impedance. Is there a way to compute it theoretically ?
Here is my circuit:
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RC/RL circuits and frequency selection
We have a lab that wants us to simulate an RC and RL circuit, and then a CR and LR circuit (series). From reading it is my understanding that reversing order of components results in reversing the ...
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Signal reflections at the driver?
This question is related to How do I use directional couplers on a differential signal?
I understand that if I have an impedance mismatch at the end of a signal cable, E.G. from a terminator which ...
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Circuit to Convert Line Level to Mic Level
How would I design a circuit that converts a line level signal to be able to be fed into a microphone input? The input impedance of the microphone jack is 2 kohms.
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Input impedance of an op Amp
I noticed that the input impedance of an op Amp is extremely high. Why is that so?
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Impedance for Helmholtz Coil Connected to Audio Amplifier
I am trying to design a Helmholtz coil, that will have an impedance of about 2 ohms (the reason for this being that I am going to hook it up to a audio power amplifier, so to get the same wattage ...
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Op amp rectifier : transfer function and output impedance
I'm working on an EE student project which uses a rectifier to keep the peak value of a sine wave.
You can find a PSpice pic of the schematics below (Ve is the input (1kHz), Vs is the output).
Op amp ...
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Complex Impedances
What does it mean to have a complex impedance?
For example, the impedance of a capacitor (in the Laplace domain?) is given by 1/sC (I believe) which equates to \$ \dfrac{1}{j \cdot 2 \pi \cdot f \...
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Interpretation of input impedance graph of a filter
I tried to simulate the input impudance of a multipass feedback low pass filter. I want to know if the graph I got is right, and if so, what does it show? Also, what is that dashed line about?
And ...
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Input Impedance calculation [closed]
I am trying to calculate input impedence of a MFB low pass filter. What I need is the symbolic expression as simple as possible so that later I fill in the values and get the impedence itself:
I am ...
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Measuring impedance
I am designing and building circuits which use 100Mb/s on a Low Voltage Differential Signaling (LVDS) bus. Some of these signals need to travel between PCBs on hand made cables. The problem is that I ...
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What is the impedance of this unusual (magnetically coupled) circuit?
Inductors X1 and X2 are magnetically coupled
M = 20 [Ohm]
X1 = 20 [Ohm]
X2 = 30 [Ohm]
I am not sure how to interpret short circuit. Is the circuit impedance given by the equation:
_Z = R1 + jX1 + ...
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Automotive Clockspring Alternative
Theoretical question: I was told by an auto mechanic friend that replacing a clockspring in the steering wheel of a car with concentric conductive rings (separate ring for each component powered such ...
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Impedance of microcontroller pins with no power supplied?
I have a serial flash chip connected to an ARM microcontroller (AT91SAM9G20). I'd like to be able to program the serial flash after both chips are soldered on to the PCB. For each of the serial flash ...
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Opamp input impedance on high frequency
I have so far used opamps for near-DC work (connecting transducers to AD and the like) and have not studied electronics in school. Now i made voltage follower based on classic LF412.
When i passed ...
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What is the physical meaning of resistance and power ratings of a loudspeaker?
What exactly does it mean when it is specified that internal impedance (or resistance?) of a loudspeaker is 16 \$\Omega\$? Is that ohmic resistance of the copper of its internal winding? Or is it ...
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How do I measure impedance of my guitar pickups?
How would I measure impedance of my guitar pickups with a multimeter? Is it similar to measuring resistance?
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Why are audio transformers required?
I was looking at simple AM radio schematics and came across this one:
As you can see it has an audio transformer. I'm still attempting to grasp the concept of impedance and such, so can someone ...
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How does impedance analyzer input capacitance influence the measured result?
I work with an impedance analyzer, measuring impedance spectra of ionic conductors. I would like to know how the obtained data can be affected by input capacitance at higher frequencies (1kHz-1MHz). A ...
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Resistance Vs Impedance?
What is the difference between the Resistance and Impedance?
When we will say it is an Impedance and when we will say it as an
Resistance?
Can you explain it with diagram (If possible) and real time ...
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Why is high input impedance good?
Naive perhaps, but
Why is high input impedance a good thing?
Is high input impedance always a good thing?
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Calculating symbolic input impedance of Multiple Feedback Low-Pass filters
I am trying to design a filter and I am Following this guide. The second step is determining the input impedance of the circuit.
The filter is a MFB Low-Pass type:
And its transfer function in s-...
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How to calculate magnitude and phase difference of impedance
How can I use a calculator to find the phase difference and magnitude of a circuit if the circuit has an impedance of, for example, \$Z = 5 + 3j\mbox{ }\Omega\$.
I have the answers \$|Z| = 5.83\$ and ...
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Controlled impedance in presence of vias and through-hole components (PTHs)
We have some controlled impedance traces on layer 4 of a board. Layer 3 is a GND plane. Layer 5 is a 3.3V plane. Both planes are unbroken (they occupy the entire layer), with the exception of vias and ...
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When does controlled impedance on a PCB matter?
Suppose I have a PCB that contains a microprocessor, or an FPGA (a "controller"). This "controller" drives a single-ended signal to an LVDS driver IC and a single-ended signal to a connector that goes ...
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Control Dielectric vs. Controlled Impedance
Can you tell me what the differences are between Controlled Dielectric and Controlled Impedance. Also what is a TDR report?
I'd appreciate it.
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How to terminate 50 ohm transmission line without drawing DC
I am sending a 10 MB/sec digital data stream by amplitude moduating a infrared quantum cascade laser. The laser requires a hefty bias of about half an amp (which drops about 8.5 volts across the laser)...
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Simplify RCL Circuit
I'm stuck with an exercise and would appreciate any hints.
I have to calculate the impedance between the points A and B:
So what I got is (starting from the right):
2L + (2R || R) + (3C || 3C)
but ...
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Attenuation - Oscilloscope Front End
I have been reading up a lot on how oscilloscopes work and how to best attenuate signals and figured the best way to learn is to create my own simple oscilloscope. My design goals are quite modest ...
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Can Z (impedance) have an φ of -105°?
Given a simple circuit with one voltage generator and one other circuit element, if these values are given:
U = 200 ∠ -45° V
I = 5 ∠ 60° A
(both values are phasors - I just don't know how to ...
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Why doesn't LCR meter measure expected reactance?
Measuring an unknown capacitor with a Tenma 72-960 LCR meter, I got 89 nF at both 1 kHz and 120 Hz, which I believe because I measured other known capacitors, too. Then I tried measuring with the ...
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Impedance Matching and Large Trace Widths
I am currently working on a design in which one of my ICs specifies the use of a 50 ohm trace. The answer to this question, Characteristic impedance of a trace, shows that a 120 mil trace is required ...
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simulate pin as connect nowhere
I am designing a measurement system based on a single pin. When the pin is connected to GND, it means move right. If the pin is not connected to anything, no action happens.
The system was ...
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line-level audio into an iPhone headset jack?
What level and/or impedance matching (or pre-amp) circuits should be used to send a line-level audio signal into the mic input ring of an iPhone headset jack with minimal distortion and/or loss?
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Art of Electronics: Emitter-Follower Zout
I am a growing frustrated with the Art of Electronics. It is such an approachable book in Chapter 1, and then in Chapter 2 it seems like the authors wanted to make it more textbook-like and they ...
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Is paying extra for "Controlled Impedance" boards necessary?
I'm doing a bit of RF PCB design, and one of the things that caught my eye is the "Controlled Impedance" option. Checking more boxes always costs more, so I want to know if this is worth the extra ...
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Input impedance
I'm trying to figure out what the input impedance of the ADF4113 is.
Looking a figure 15, I'm not sure how to read that.
In my setup input is on RFinA and RFinB if connected to GND via a 100pF ...
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computing Impedance related with Voltage Vx
I have a circuit like:
How do you get Thevenin ( \$V_x = I_x * R\$) circuit?
I have these formulas, but I am a little stucked...
\$\ I_0 + Ix = (\frac{V\pi}{r\pi}) + gmV\pi \$ ...
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50-ohm trace impedance
I've just calculated trace parameters so that it would have 50 Ohm impedance on PCB.
Then I've noticed, that its impedance does not change when I make line longer or shorter as long as I leave trace ...
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Do I need to control trace impedance for DDR2 memory?
I am going to try to interface low-speed 8bit DDR2 chip to FPGA, and I've got some questions crucial to make it work :-)
3) What is up with controlled impedance of PCB traces? Why it's important? ...
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ADC input circuitry and source impedance
I'm using a maxim ADC in my application from this family: http://datasheets.maxim-ic.com/en/ds/MAX1304-MAX1314.pdf
The devices have relatively low input impedance. If you look at Figure 5 in the ...
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