Questions tagged [impedance]

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

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Are frontend amplifiers in RF transceivers impedance matched?

I think by now I get complex impedance, the Smith chart, and antenna matching, but I am wondering how in an RF transceiver, i.e. a radio, the amplifiers on the transmitting and the receiving end are ...
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Twin-T notch filter with high input impedance and low output impedance using one op-amp

I have a very space and power constrained application, where I want to apply a twin-T notch filtering to an audio signal and add a little gain of about ~10x. The following filter section has the ...
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Differential Microstrip Impedance Calculators Giving Conflicting Answers

I am attempting to determine the trace width needed for routing a differential signal of 100 Ω on a PCB I am designing. This is a hobby project and the differential traces are for gigabit ethernet. I'...
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Do I need a GPS simulator to design a device that contains a GPS receiver and a pre-designed antenna?

I have designed a device using an STM32 Nucleo board, a GPS module, a GSM module, some discrete components, and a bread board. It is a sort of a car tracker. I have decided to design my own custom ...
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Unexpected impedance spike when paralleling capacitors

I was watching a video from EEVBLOG about bypass capacitors, and he presented a theory that randomly connecting different values of capacitors in parallel can create unexpected impedance spikes: To ...
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Creating equivalent impedance for given measured frequency response (that does not involve blind trial-and-error)

I have a measured frequency response and I would like to create an equivalent impedance model for it. I start with a parallel RLC and then add series R and series L to the elements. I blindly tune the ...
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Magnitude and phase of parallel RLC with series resistor

I have been looking for a while for this issue, but unfortunately I am bit stuck on getting the magnitude as well as the phase of a RLC circuit with a series resistor, seen from V1 (see picture). ...
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Which matrix index should be used when Y (admittance) is shown to compose a circuit segment mapped to an ABCD matrix? Y21? Other?

I would like to cascade a serial capacitor with a shunt inductor to form an L-match network by multipling two ABCD parameters and convert the result to S-parameters that represent the composite ...
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How do the 5 elementary two-port networks map to unbalanced networks with a common ground?

Background (questions below) I've been trying to understand how to use S/Y/Z/A-parameter matrixes to create circuits mathematically with 2-port components in series, parallel, and ground-shunt. For ...
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What does \$\beta\$ represent with respect to the length of a transmission line?

The picture below shows the ABCD parameters for a transmission line of length \$l\$ from this video. Question: What does \$\beta\$ represent?
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Current sensing using transimpedance amplifier

I am looking for a way to create a Transimpedance Amplifier like below (to convert current to voltage) The problem now is how to add the current source? The current I want is the one read from ...
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Is there a way to sense the characteristic impedance of a transmission line?

Is there a way to sense the characteristic impedance of a transmission line? If a transmission line between a driver and a receiver is 50ohm, is it possible to design a circuit at the receiver end to ...
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How is the characteristic impedance of a transmission line sensed according to this paper?

This paper proposes a method to sense the characteristic impedance of a transmission line. How is it done? I don't understand the explanation given. Does anyone understand it?
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When do we add a resistor between the inverting and non-inverting terminal of an op-amp

simulate this circuit – Schematic created using CircuitLab In the above image, let's assume for namesake that the op-amp is powered and there are inputs at both the terminals. My question is , ...
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Are T-parameters the same thing as ABCD parameters?

S-parameters can be converted to either T-parameters or ABCD-parameters, and both are considered a "transfer matrix". The conversion from S-parameters to T- or ABCD-parameters are defined ...
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Reduce Resistance and Heat Dissipation in a fuse

I have a 240VAC, 200A switch. It has very tight space requirements, and has to be sealed - so no external air flow. I need to minimize heat as much as possible. I have redesigned bus bars, spacing, ...
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Can admittance (Y) be used to calculate reactance when L and C values are calculated from the Y12 and Y11 parameters like normal as X=XL-XC?

My original question sought to understand the relationship between S-parameters and reactance. In the process of trying to figure that out, this second question arose. The actual question is at the ...
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Designing of a ribbon microphone (sort of) output transformer

I'm currently working on an experimental string musical instrument. It isn't my invention though. The source of inspiration called Dvina has an unusual pickup system. It senses the current induced in ...
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How are S-Parameters and Reactance related, can one be calculated from the other?

I know that, for example, \$X_L=2\pi f L\$ will calculate reactance of an ideal inductor, but can this be calculated for a real component model? Given the S-Parameter values at some frequency from an ...
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4 answers
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Is the resistive component of impedance the same as DC resistance for a given component?

If I calculate the impedance of a component in an AC circuit as Z=V/I, will the resistance component of that impedance, ZcosΦ, be the same as the resistance when that same component is in a DC circuit ...
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Method for building a test fixture for the 4294A impedance analyzer?

I have an Agilent 4294A, a 40Hz-110MHz impedance analyzer, but no test fixtures to use. Unfortunately the official test fixtures are out of my price range so I need to build some. After reading ...
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How would you find the impedance of this circuit? [closed]

I am working on a project using C++ to find the impedance of a circuit. In implementing the program I have realised that the program cannot find the impedance for a circuit of this type. My intuitive ...
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Should I use one thick wire or many thin wires in a step-up high frequency transformer to reduce resistance and impedance?

I am planning to make a step up high frequency (hundreds of kHz) transformer. I want to reduce the resistance and impedance in the secondary. Should I use one thick wire in the secondary, or should I ...
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Design challenges with high input impedance amplifier

After a couple of days of reading (also trying to find similar posts) and trial and error in my simulation tool (TINA) I see no other way than consulting you experts. In my application I have a sensor,...
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Can the frequency of voltage change throughout a circuit?

I am currently doing a project which involves taking a circuit of resistors, inductors, and capacitors (combined in any way imaginable) and finding the total impedance of the circuit. For the latter 2 ...
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Converting measured S-parameter to Z-parameter does not match the Z-parameters measured on the same circuit

I have measured the S-parameters for a 4 port circuit. For a certain frequency those values are: ...
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1 answer
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How to measure output impedance of this circuit?

I have the following circuit with an operational frequency range of 100 - 10kHz, always square waves. How do I measure the output impedance? I have access to an LCR meter (BK Precision 891.) Do I ...
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A non-inductive behavior in low frequency of an inductor

I have a question that has been torturing me for a while now. I cannot give you guys all the information, however, what I can say is that I have this measurement of an impedance of an electrical ...
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1 vote
1 answer
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Homework: impedance equivalence with transformer

I am working on this homework problem and I am wondering if my approach for finding Zeq is correct. I know my matrix is correct, but I feel like I need to do something else to find the correct ...
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How to calculate the differential impedance from an s-parameter file

I have an s4p Touchstone file with a reference impedance Zr, then I think the differential impedance should be as below but I am not sure because I am not sure what the meaning of the reference ...
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Fault impedance type?

Usually fault impedances are resistive type. But is it possible to have a mix of resistive and reactive component in fault impedances? Looking at many simulation tools, they give the possibility to ...
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4 answers
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Question about the BJT emitter resistance

I'm trying to teach myself a little bit about BJTs, particularly through the Art of Electronics. I came across something I've been trying for days to wrap my head around. (page 92, third edition) I ...
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1 answer
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Independently control LEDs in series with intermediate point

I bought a bunch of LED bar arrays (DD-12 GWB KINGBRIGHT), with a relatively strange wiring diagram. I would like to control each LED. It's easy for LED A, but B and C for example are wired together. ...
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What would the output impedance of the circuit below be?

My analysis is as follows, the auxiliary amplifier with input Vb is being used to sample the output current of the main amplifier (NMOS on the bottom) and return a voltage to its gate. So it is ...
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1 answer
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What are the recommended differential trace characteristics for Power over Ethernet input section?

I've been looking through a few application notes for Power over Ethernet front ends such as Microchip AN3468 and Skyworks AN1130. I can't figure out what the characteristic impedance of the ...
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0 answers
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How to calculate the output impedance of an oscillator?

Is it possible to approximately calculate the output impedance of an oscillator if the rise/fall times at a given load capacitance are known, simply by using the formula for the RC time constant T = R ...
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2 answers
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Is a high resistor value between GPIO pads acceptable?

I'm designing a PCB which involves integrating two microcontrollers - an ATSAMD51 (Cortex M4)-based Arduino, and a Raspberry Pi. I need to connect a parallel bus of 10 signals between the two devices. ...
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-1 votes
1 answer
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Body voltage from stray capacitance

I've been learning about stray capacitances in my electronics module and was trying to apply the concept. If I were to hold a mains wire, consisting of a live, neutral and ground, and there were stray ...
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2 votes
0 answers
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Small signal output impedance for a circuit with bipolar transistor?

For the following circuit, I need to find the small-signal impedance looking into the collector of the transistor at terminal X, not taking the load resistance Z into account: My attempt at a SSM is: ...
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1 answer
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Characteristic impedance when routing differential

Can the characteristic impedance value of a single-ended transmissions line be omitted when the two transmissions lines of a differential pair are routed differentially (not two isolated lines)? I ask ...
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1 answer
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Does adding a "spare" ribbon cable to a PCB increase trace impedance?

I've read numerous posts advising that trace length must be kept short on a high speed board to reduce the effects of impedance. If my traces are routed through a pin header that has an IDC ribbon ...
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-2 votes
1 answer
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Why does this method of measuring inductance work? [closed]

I recently watched this video from EEVblog showing a method of measuring inductance. I'm probably missing something obvious, but why does this work? Mathematical proof would be great. Thanks. https://...
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1 vote
2 answers
98 views

Transfer function for Sallen-Key notch filter

How can I find the transfer function H(s) of the following circuit by using impedance of the circuit? Should I instead do it by nodal analysis?
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3 answers
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Differential stripline characteristic impedance measurement

How would you measure the characteristic impedance of a differential pair (stripline) if you don't have access to a Vector Network analyzer? I have access to an oscilloscope and a signal generator. ...
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3 answers
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What effect does a splitting an audio signal using a y-cable have on that audio signal?

Given a clean instrument-level audio signal of reasonable amplitude passing from point A to point B via a TR/unbalanced cable, what effect would replacing that cable with a TR to dual TR cable running ...
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Voltage Follower not working for low resistance loads

I have simulated a bridge-tied load, which is to be tied to an ultrasonic transducer. The part I'm worried about is the part where the BTL touches the transducer itself. As one can see, the ...
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2 votes
1 answer
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I need help understanding what the total Impedance in a delta connection is

I'm trying to upskill by teaching myself electrical engineering. I already have a degree in Theoretical physics and Pure mathematics so I don't mind math heavy answers and don't find the math's of the ...
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3 votes
2 answers
130 views

Can VSWR be complex-valued or is it always real?

This question is related to this one, but about VSWR instead of return loss: Can VSWR be complex since it is based on a complex-valued \$\Gamma\$? If VSWR is complex then it is worth noting that: \$\...
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Is there a spec for maximum voltage drop to a motor at startup?

When an induction motor starts, it pulls more current than when continuously running. Current flow causes voltage at the terminals to drop. At some point, the voltage drops too low to successfully ...
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0 votes
1 answer
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What is the difference of meaning between the phase angle of S11 and the phase angle of Γ (Gamma)?

I realized recently that the Touchstone "DB" S-parameter format (.s1p, etc) uses the phase angle of \$\angle \Gamma\$ instead of \$\angle S_{11}\$ and wondered why it didn't use the phase ...
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