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

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39 views

Calculating resistance and reactance of an coil (motor winding)

I want to find out the resistance and the reactance of an motor coil. I can measure the magnitude of the current through the coil using a DMM. For example, If the voltage across the coil is 230v ac ...
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0answers
21 views

How to measure the impedance of Induction motor windings

I want to know the easy method of measuring the impedance of induction motor windings (coils) in rectangular form. Say, Z=R+jXL; need to identify Z, R and XL as accurate as possible
11
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2answers
499 views

Should each trace carrying RF be 50Ohm in characteristic impedance? How?

I have to translate a VHF (160MHz) receiver schematic into a PCB. After looking here and there, I am a bit confused. It seems like the main issues with RF are to avoid stray inductors and ...
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1answer
36 views

Interfacing a GPRS chip (WISMO218) with an RF antenna. Calculating line width for the right impedance

I want to interface the WISMO218 GPRS chip with an antenna. The antenna lines on the PCB board have to be very specific, otherwise the system won't work. I have uploaded the part of the datasheet that ...
3
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2answers
249 views

Finding the schematic of a black box with unknown impedances

I'm struggling with trying to understand a piece of homework in Electrical Engineering that I'm really trying to solve on my own but now I'm basically stuck. The assignment is to find the schematic ...
2
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2answers
37 views

Solving for the impedance and phase shift in a series-parallel AC RCL Circuit with Complex Numbers

Having a lot of trouble working through an AC circuit, asking for some help. The circuit is relatively simple - I have a capacitor of capacitance \$C\$ and resistor of resistance \$R\$ hooked in ...
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1answer
41 views

Why does ceramic capacitor ESR change with frequency?

In most datasheets, I see a typical table which shows that ESR of ceramic capacitor changes with frequency. I understand that impedance of every kind of capacitor must have a minimum due to its ...
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3answers
70 views

What is Source Impedance?

I was going through data sheets of op amps and saw that bias currents usually add unwanted voltages due to voltages generated from the bias current flowing through the source impedances. What exactly ...
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3answers
148 views

How do utilities calculate transmission lines impedance?

I'm an electrical engineering student getting into Transmission Circuit Analysis, and a question came out to me: How do utilities measure their transmission lines impedance? Do they use special ...
2
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1answer
52 views

Matching the impedance of a filter?

Currently designing a circuit consisting of 50 Ohm rated ICs. Between two ICs (switches), I will place a BP-filter made out of discrete components (high-Q inductors and capacitors). The filter will ...
0
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2answers
58 views

Output Voltage Swing vs. Load Resistance of an Op Amp

What does the "Output Voltage Swing vs. Load Resistance" signify? Lets say I want to get a gain of 400 from an op-amp. I can use any one of the following combination Gain = -(R2/R1) Case 1: R2 = 400 ...
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3answers
82 views

How do I find the input impedance a common emitter amplifier?

How do I find the input impedance of this common emitter amplifier? \$V_{CC}\$ is supposed to be at the top of \$R_5\$. I forgot how to do the analysis to find the input impedance. The input goes ...
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4answers
92 views

What is an impedance in AC circuit? (Preferred simple answer) [closed]

Can someone please help me understand what an impedance in AC circuit, please? I have read so much about it still I having time understand it. How does it affect the circuit, is it good or bad for ...
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votes
1answer
68 views

Question regarding electrical resonance/impedance [closed]

Me and my friends are currently working on a project where we have basically soldered a microphone unto a circuit with a small laser pointer. We have a reciever circuit consisting of a photo resistor ...
2
votes
3answers
171 views

How can I analyze an op-amp based negative impedance converter in a circuit?

I am thinking of the circuit pictured below, which, while the op-amp is operating in its linear region, gives rise to the relation $$ v_0 - v_1 = -i_0 r , $$ where the direction of positive current ...
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1answer
64 views

Wind high impedance transformer at home

Suppose I need to make transformer at home, but I am unable to wind 100k turns obviously, then can I just connect a resistor in series with a winding to achieve desired impedance? Will it have serious ...
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2answers
109 views

Output Impedance of BJT/Mosfet amplifiers

I have heard in lectures that the desired output impedance for the BJT/Mosfet Amplifiers is LOW. But these transistors are Transconductance amplifiers 'by birth'. I mean they give output current ...
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2answers
74 views

What is the 'characteristic frequency' of a certain impedance?

I'm not familiar with that term. Could somebody explain it to me? Is it the frequency at which the phase of the AC current running through the impedance goes to zero? Edit: Here is the context in ...
2
votes
1answer
54 views

impedance matching single vs series capacitor

Im looking at a impedance matching circuit on a schematic that shows a .75pF capacitor pulled to ground. With my current board design I have a 1pF and a 3.3pF on the board already so I am thinking ...
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0answers
70 views

From RLC prototype to signal flow graph

This simple 3rd order low-pass circuit simulate this circuit – Schematic created using CircuitLab can be described with the following 3 equations: $$-V_1 = \displaystyle \frac{-1}{sC_1} ...
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2answers
152 views

How to measure trace impedance?

I have seen that trace impedances in PCB's are maintained 50 ohm & so on. How to measure this impedance using a simple multimeter?
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2answers
102 views

Why is power reflected when there is an impedance mismatch? [duplicate]

I understand that when there is an impedance mismatch between an output stage, for example from an amplifier, and an input stage, for example, a transducer; power is reflected. I would like to know ...
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2answers
112 views

Op amp circuit design

I am having trouble with understanding how to design circuits involving op amps. I need to design a circuit using as less op amps as possible which has the following characteristics: high input ...
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1answer
37 views

How to determine the minimum proximity of magnet to an AC line for no electrical impedance?

As the title says, I am wanting to calculate the minimum proximity for a magnet to be near a AC line for no electrical impedance. My scenario is this: I have a theoretical device like MagSafe ...
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3answers
213 views

Do I really need the open loop output impedance of an op amp?

There are several answers on the internet and here on how to calculate the output impedance of the opamp with a given feedback. My intention, though, is to find this value with an open loop ...
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1answer
69 views

Estimating the schematic of a black box using the measured impedance curve

I need to estimate/predict the circuit design of a black box using the measured impedance at the output of this box. The only hint I have is that the circuit inside the box is a demodulator. Is it ...
0
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2answers
89 views

OUTPUT Impedance

I wish to find the output impedance of the circuit in the attachment. I have drawn the AC Equivalent of the circuit but I don't know how to come out with the Formula for the Output Impedance. I would ...
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1answer
291 views

Differential pair impedance calculation

I'm having troubles calculating the characteristic impedance of USB/Ethernet traces for a pcb. The Saturn PCB design program calculates values where I'm not sure if they are correct. I want to use a 4 ...
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0answers
46 views

2SC1970 input impedance

Looking at this circuit, it says the base impedance is 12 ohm, so he used a 2:1 transformer to match to the input 50 ohm. Now in the spec of 2SC1970, base impedance is 10.4-15.3j ohm, but why did ...
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6answers
996 views

How does Ohm's law extend to Z if Z is complex?

We know that impedance, Z, is complex. I'm told that $$V = IZ$$ But that rearranges to $$Z = \frac{V}I$$ But both voltage and current are real numbers, so how can a real number divided by another ...
2
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2answers
113 views

50 ohm output impedance

I saw some circuits that uses a emitter follower as a buffer for output. The emitter resistance is 470\$\Omega\$. The author says that, since the ac emitter resistance is very small, he put a ...
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1answer
63 views

MHz oscillator probe impedance?

I find something weird going on in my 100MHz oscillator probe. I always thought the probe has a resistance of 1M ohm, but apparently at 13MHz, when I put a 2.2k ohm resistor in series with the probe, ...
2
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2answers
54 views

How differential pairs should be called out on fabrication print?

I have a design that the diff-pairs (100 Ohm impedance) and single-ended (50 Ohm impedance) are routed on the same layer. To specifying the impedance, on the “Lamination Stack-up”, I am going to add ...
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0answers
36 views

Reaction vs Rotary torque sensor for force/impedance control

I am working on a robotic system that is requiring a torque feedback from a rotational (single axis) joint for a force or impedance control loop. When researching the available torque sensors I've ...
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1answer
65 views

Replace crystal earpiece in bat detector circuit

I've been following the instructions on http://pw1.netcom.com/~t-rex/BatDetector.html which includes the following schematic for a Frequency Division Bat Detector circuit: The instructions clearly ...
2
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1answer
63 views

Impedance of waveguides shorter than 1/10 of wavelength

I read already several times that it is a common rule of thumb, that matching the impedance of a waveguide to the external network impedance is only necessary for waveguides longer than 1/10 of the ...
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1answer
94 views

Sinusoids and Phasors AC circuit impedance

Hello. I've been doing problems, and transforming from time domain to phasor domain to find input impedances seems simple enough But I've come across a circuit with a dependent voltage source, as ...
2
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1answer
88 views

Impedance Matching of Antenna and Amplifier

I've been doing a lot of research on impedance matching and I am just having a hard time understanding some of the specifics and I was wondering if someone here could help me out. I have a 50 Ohm ...
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1answer
63 views

How does one calculate the voltage ratio V+/Vo for this circuit?

I can understand the first case above, that seems simple as I can simply measure across the ground and V+, but I am getting very confused for the second case. Is the capacitor and the resistor in ...
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1answer
58 views

How do I wire speakers in multiple rooms to one amp? [closed]

I would be happy if anyone can help me with the following project I wish to build : I have an old amplifier 4ohm impedance with A and B zones, support for mono and stereo and playing both A and\or B. ...
1
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1answer
114 views

How to calculate theoretically Output Impedance of a Linear Voltage Regulator

I am trying to calculate the output impedance of the following circuit, a linear voltage regulator. What is confusing me is the feedback coming from R1 and R2. I used R4= 500 ohms, R3 = 1K , R1= 25k ...
3
votes
2answers
169 views

What is the output impedence of this RC Circuit

I have this simple circuit. And from what I calculated the output impedance seen from the OUT node comes to about \$138.765 \Omega\$. $$ X_c = \frac{1}{2\pi * 890*10^3 * 10^{-9}} = 178.8257\Omega $$ ...
5
votes
1answer
114 views

Placing Via's on PCB

I'm designing a PCB for USB 3.0, the specifications for Differential impedance comes at 90 ohms with a tolerance of +- 5 ohms. I've used different calculation tools but when I have to hold these ...
9
votes
4answers
510 views

How is it possible to have a 5W transmitter driving 50 ohms with a 12V supply?

So let's say you have a circuit, which generates a carrier wave at some frequency (let's say 27MHz) and it's connected to a 50 ohm dummy load (which I gather is equivalent to an antenna for circuit ...
1
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4answers
89 views

Current Source Circuit Internal Impedance

So I've been learning about current source circuits - this one in particular. I'm told that an ideal current source should give out the current no matter what happens to the load. But it should also ...
10
votes
2answers
379 views

Why does ST recommend 100nF decoupling caps for a 72MHz MCU? (And not 10nF)

I've been reading about decoupling caps, and I can't seem to understand why ST recommends 100nF decoupling caps on a 72MHz arm mcu. Usually 100nF decoupling caps are only effective up to about ...
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3answers
134 views

Recognising output impedance of an amplifier though inspection

The output impedance of FET amplifiers seem to be a hit and miss affair when I try to find it just through inspection. For example, sometimes it's easy to predict, whereas some other times I have to ...
0
votes
0answers
34 views

How does the impedance of the source effect the positive sequence impedance measurements of distance relays?

How does the impedance of the source effect the positive sequence measurements of distance relays in relation to power system protection? I wrote that increasing the source impedance decreases the ...
2
votes
2answers
95 views

Balanced line impedance matching

Is there a way to convert a 100Ω balanced connection to a 200Ω balanced connection without using two baluns? I have a 2.4GHz baseband that I want to attach to a front end, but the baseband ...
2
votes
3answers
212 views

Low output impedance vs high output impedance of an amplifier

I read that a low output impedance is desirable for an amplifier. I am unable to understand why from my analysis of the output side of the common emitter amplifier. So looking at the output of the ...