Questions tagged [impedance]

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

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1 answer
657 views

Xilinx FPGA and DDR3 Memory. Confusing Impedance combinations

Currently I'm planning on doing a PCB with DDR3 memory and an Artix7 FPGA. During my research a few questions accumulated. When looking at the reference manual of the Arty7 board, I see that I have to ...
1 vote
2 answers
67 views

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 ...
1 vote
2 answers
51 views

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 ...
4 votes
4 answers
178 views

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 ...
3 votes
1 answer
2k views

Output impedance of a series shunt feedback amplifier

I am trying to find the output impedance of a series shunt feedback amplifier by converting it to a two port network. I know the input impedance: Ri=ri*(1+A.β) But I dont know how I should find ...
1 vote
2 answers
898 views

What if the primary coil of a transformer was connected without the iron core and the secondary coil?

I'm trying to create an electromagnet from a microwave oven transformer. The secondary coil will be removed, and the top of the transformer (The I in the E-I transformers) will be sawed off (to ...
8 votes
4 answers
607 views

Transmission Line Transient Response To Step Voltage Prior To Any Reflections

This question seeks a definitive and precise answer to a question regarding the transient response of a transmission line. Figure 10 of TI Application Note snla026a contains a graph showing (among ...
13 votes
4 answers
39k views

What does it mean for reactive power to be delivered / consumed?

Real power makes sense since there is actual consumption, but regarding reactive power; what is consumed / delivered? And how does the circuit change once this happens?
1 vote
1 answer
42 views

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'...
0 votes
2 answers
92 views

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 ...
2 votes
3 answers
269 views

Circuits of AC - impedance

I have a question regarding impedances. While it is intuitive that \$ R \$-element has impedance \$ R \$, it's not so easy for me to figure out impedances of \$ L \$ and \$ C \$. Here is my, probably ...
6 votes
2 answers
3k views

Will a 75ohm cable work with (not break) a 50ohm gsm shield?

I need to have a long (100') stretch of cable from my antenna to a GSM box (remote control for heating via GPRS or SMS), and I need to minimize signal loss. In another (totally different) question ...
1 vote
3 answers
3k views

Low impedance voltage testing (LoZ)

Is there any issues with using low impedance mode on a multimeter for day to day testing on mains voltage 240Vac or if this mode should only be used when testing for phantom voltage? Is there any risk ...
-1 votes
1 answer
67 views

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). ...
-1 votes
1 answer
42 views

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 ...
7 votes
3 answers
719 views

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 ...
2 votes
1 answer
49 views

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 ...
0 votes
0 answers
16 views

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 ...
0 votes
1 answer
38 views

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?
7 votes
4 answers
772 views

How is transmission line impedance selected?

I understand (roughly) why transmission line impedance has to be matched to the source and the load. What I don't understand is how different technologies have chosen to use different impedance. (...
0 votes
2 answers
209 views

Typical impedance values for a large 150 MVA power transformer

I am trying to calculate the impedance in ohms for a 220kV/110kV 150MVA transformer (European grid), but the values I am getting are not in range of values I usually see in online examples. X in p.u....
0 votes
1 answer
37 views

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 ...
1 vote
3 answers
77 views

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 ...
1 vote
2 answers
53 views

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?
1 vote
0 answers
71 views

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 ...
3 votes
3 answers
511 views

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 , ...
3 votes
1 answer
82 views

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, ...
0 votes
1 answer
35 views

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 ...
0 votes
1 answer
58 views

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 ...
1 vote
0 answers
36 views

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 ...
2 votes
4 answers
627 views

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 ...
1 vote
1 answer
205 views

RF via impedance calculation with NFP removal

I'm trying to match the impedance of a RF via from bottom layer to top layer in a 6-layer PCB design. GNSS signal. Unused pad (NFP) removal activated. The selected via size is 0.9mm pad and 0.5mm ...
0 votes
1 answer
115 views

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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0 answers
42 views

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 ...
-1 votes
1 answer
93 views

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 ...
0 votes
0 answers
52 views

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 ...
2 votes
1 answer
59 views

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 ...
0 votes
1 answer
67 views

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: ...
6 votes
2 answers
578 views

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 ...
0 votes
5 answers
450 views

How can I minimize the variance in voltage drop across transistors - or eliminate transistors from this design?

I have a fairly simple circuit that I'm using with an arduino to measure the impedance on a very low-resistance circuit. The user plugs in a device at A and B and the arduino can compute the ...
1 vote
2 answers
419 views

Thevenin Impedance for network with only dependent sources

If a network has only dependent sources, you need to use a test current source or test voltage source (1v, 1a, something simple) since Zth = Voc/Isc doesn't work. Is it valid to use a DC source as a ...
1 vote
2 answers
89 views

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 ...
3 votes
4 answers
187 views

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 ...
1 vote
1 answer
76 views

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 ...
0 votes
1 answer
100 views

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 ...
0 votes
3 answers
290 views

Determining changing values of C in RC circuit

My problem is related to the change in the membrane capacitance of a cell (link to paper). The electrical properties of the cell can be modeled using a battery, a resistor and a capacitor in series. ...
0 votes
1 answer
2k views

Calculation of common emitter output impedance with output resistance

[ I don't understand why \$g_{m}\$ survives. Since \$v_{\pi}\$ is equivalent to \$\Delta V\$ , which is perturbation of signal, which is then set as AC ground. Doesn't that mean \$v_{\pi}= \Delta V = ...
1 vote
1 answer
67 views

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 ...
1 vote
2 answers
317 views

How to convert this single ended output to a precise impedance balanced output?

This amplifier suits my purpose with one matter that I couldn’t figure out. Its output impedance is given as 0.01 Ohm. The output of this amplifier will be coupled to a very high input impedance(more ...
0 votes
1 answer
187 views

Impedance Matching Network with tracks+connectors in between (practice)

I've been struggling on how to design (and develop in practice) an impedance matching network with some traces/tracks/paths (whatever you wanna call it) and some connectors in between. So here is the ...

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