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

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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
80 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
83 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
32 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
139 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
45 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 ...
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2answers
83 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
132 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
35 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
953 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 ...
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2answers
84 views

50 ohm output impedance

I saw some circuits that uses a emitter follower as a buffer for output. The emitter resistance is 470 ohm. The author says that, since the ac emitter resistance is very small, he put a 50 ohm ...
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1answer
56 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, ...
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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
20 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
53 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 ...
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1answer
48 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
43 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 ...
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1answer
73 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
61 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
50 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. ...
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1answer
48 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 ...
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2answers
157 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\$. $$ X_c = \frac{1}{2\pi * 890*10^3 * 10^{-9}} = 178.8257\Omega $$ ...
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1answer
97 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 ...
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4answers
427 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 ...
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4answers
79 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 ...
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2answers
310 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
116 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 ...
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0answers
32 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 ...
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2answers
79 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 ...
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3answers
100 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 ...
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2answers
156 views

Most efficient and rigorous way to calculate input/output impedances (transistor circuits)

I've always had troubles with input and output impedances. It is not very well explained anywhere else I could look on the web so... What is the most efficient and rigorous way to calculate input and ...
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2answers
88 views

Adding voltage divider to output of power amp concerns

I have a load box I use to test and burn in analog audio power amplifiers. Each load box is tailored for a specific amplifier circuit and for one of the load boxes I would like to add an LED that ...
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1answer
61 views

Impedance line matching and component value matching

I have the following circuit for the SIM900's antenna connection, using the A10393 antenna from digikey: In closer look: First of all my knowledge on RF design is not great. My questions now are ...
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1answer
113 views

Is RF Transformer Impedance Significantly Affected by Wire Size?

I'm building a Softrock Ensemble III HF Receiver. The online instructions are pretty good, but have a few remnants from an earlier version that no longer apply. So, despite the discussion about the ...
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42 views

Impedance Matching for Amplifier Output [duplicate]

0 down vote favorite I needed some basic advice about impedance matching. I have an RF amplifier with 50 ohm output impedance, capable of generating 400W output power at 500kHz. I am trying to ...
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4answers
187 views

Impedance matching for amplifier output

I needed some basic advice about impedance matching. I have an RF amplifier with 50 ohm output impedance, capable of generating 400W output power at 500kHz. I am trying to deliver this to a 12 ohm ...
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1answer
48 views

Output impedance of a differential line receiver

Let's say I have an INA134 (http://www.ti.com/product/ina134) from Texas Instruments in my design. I want to take the output of that IC and feed it into a resistor network which can have a flexible ...
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1answer
86 views

Does coil require extra resistor before connecting mains?

I am planning to build diaphragm air pump. For this instead of using an AC motor, I am planning to connect an aluminium rod to diaphragm, and put a permanent magnet on it that will be pulled and ...
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3answers
99 views

Simulate RF transmission lines at Low frequencies

I would like to simulate RF transmission lines in how they propagate, and how impedance mismatches at the end of the transmission line cause reflections and power transfer does not work. It would be ...
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2answers
131 views

Question with solving for complex power, S, for each component

simulate this circuit – Schematic created using CircuitLab Hi! So I have a couple questions that I have already tried to solve that I think I am going in a little bit of the wrong ...
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3answers
242 views

Impedance matching an RLC circuit (inductor macroscopically drawn on PCB)

Context: I am a physics grad student with basic knowledge of circuits, but impedance matching and RF domain are beyond my normal scope. My PCB is actually copper bonded to a ceramic substrate that is ...
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2answers
94 views

Phototelectric smoke sensor with microcontroller

I am trying to connect a photoelectric smoke sensor with Atmega328. The smoke sensor IC has pin 7 as the I/O pin which gives a 9V when smoke is detected. I have connected this pin to the input pin of ...
0
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1answer
65 views

Running single-phase through two or three windings of a three-phase inductor; why does the direction of the middle winding matter?

I have a three-phase inductor, MTE RL-00403, nominal 9 mH. I have some experimental results that don't make sense to me, which appear to be related to the fact that all three chokes share a single ...
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0answers
48 views

Crystal Oscillator output voltages and power

I have built the crystal oscillator stage to the Pixie 2, a Hartley oscillator, with a 9 volt voltage source. I measured the output with my VOM set to AC 30 volts. It read almost 30 volts. That is ...
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1answer
52 views

According to impedance bridging principles, are these results accurate?

Here is the relevant data The setup for this experiment was a Shure SM57 dynamic microphone routed into a Magneto Audio Labs VariOhm, a variable load impedance device, which was then routed into a ...
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3answers
129 views

Output impedance refers to open circuit o/p impedance or short circuit o/p impedance?

When we specify output impedance of a two port network, does it imply open circuit output impedance or short circuit output impedance? Wikipedia: output impedance ; Wikipedia: two-port network g22 ...
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2answers
61 views

Why is there no voltage drop along a feedline

This page shows a graph of voltage along a transmission line by distance. Considering the case of a simple purely restive feedline of 50 ohms matched to a load of 50 ohms, I would expect the voltage ...
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1answer
79 views

Wien Bridge Frequency Selective Network Frequency Response Proof Exam Question

So this is part of the solution to the proof of what the frequency response on the frequency select section of the Wien Bridge oscillator. What I don't understand is how the answer are equal to ...
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2answers
155 views

Calculating Z_T (total impedance)

Using a mobile device so I can't upload a picture. I need to find Z_total in a circuit. I will simplify the circuit description so that its easily pictured. The simple circuit contains The ...
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2answers
133 views

BJT circuit analysis confusion

In the following circuit: Ib is given as: I don't understand how they arrived at this. I thought it would be a voltage divider between Rsig and Rb||Rbase divided by Rbase: Can anyone explain? ...