# 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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### 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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