Tagged Questions

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

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1answer
58 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
34 views

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

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
60 views

Output impedance of an IC [on hold]

I want to use an IC as a power amplifier to drive a broadband piezo transducer. I need to know the output impedance of the IC for the purpose of Impedance matching. I think because the power amplifier ...
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1answer
36 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
132 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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votes
1answer
84 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
375 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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3answers
54 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
248 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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1answer
77 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
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0answers
31 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
72 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
63 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 ...
2
votes
2answers
111 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
76 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 ...
0
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1answer
45 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 ...
2
votes
1answer
77 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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0answers
19 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
153 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
41 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 ...
0
votes
1answer
81 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 ...
1
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3answers
81 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
101 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
174 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
73 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
votes
1answer
55 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
43 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
51 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
122 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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votes
2answers
58 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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votes
1answer
62 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
143 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
123 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? ...
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1answer
87 views

Output impedance of current series feedback BJT amplifier?

So according to what I've read, in a common emitter BJT amplifier, an unbypassed emitter resistor acts as a current-series feedback path. The gain without feedback is: ...
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2answers
158 views

Extremely low output from amplifier

I am unsure what is wrong with my amplifier / microphone coupling. I have read many of the posts on stackexchange including the following: ...
2
votes
2answers
156 views

How does Altium Designer's “impedance constraint” feature work?

Altium has a design rules option for setting a track width constraint according to line's impedance (e.g.; 50\$\Omega\$). How do I use it? Please give me instructions or a link to an online tutorial. ...
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2answers
88 views

Why Inductor reactance 180 ohms?

Why is the inductor reactance 180 ohms for designing Voltage controlled Oscillators ( or oscillators maybe ?) I came across a few resources for designing oscillators, colpitts and hartley ...
4
votes
1answer
100 views

What does 100Ohm @ 100MHz exactly mean in ferrite beads?

I am trying to understand the parameters of ferrite beads and having trouble in understanding the impedance vs frequency parameter. What does 100Ohm at 100MHz exactly mean? Does it mean that the ...
4
votes
1answer
172 views

Calculating differential PCB traces - Edge-Coupled Microstrip

I finally have the microstrip characteristic impedance thing figured out. But now, of course, I need to learn about differential signalling on PCB traces. I've spent some time researching. Here is ...
0
votes
1answer
346 views

Coplanar waveguide for differential trace calculator

Although there are plenty of free impedance calculators out there, I'm struggling to find one that can solve impedances for a differential pair using coplanar waveguide. Anyone know of any free ...
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0answers
90 views

Calculating Voltages in phases when a neutral fails

In the above star-connected three phase circuit the neutral is floating. I need to find the voltage across each load and which voltages are higher than 240 (Assuming the Line-to-line voltages are ...
0
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2answers
155 views

Finding the Average Power Loss in a Series RL Circuit

Question : A current \$I=3\sin(400t)\$ amperes in a series RL circuit in which \$L=1mH\$ and \$R=100Ω\$. What is the average power loss? Answer : $$ APL = 450 \space W $$ My Steps : ...
1
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1answer
54 views

dual piezo pickup

I experimented with different types of piezoelectric disks as double bass pickups and found two that picked up different parts of the frequency spectrum decently. The specification of the two piezos ...
2
votes
2answers
198 views

Using audio amplifier speaker output to drive an electromagnet

My first time here as a poster so forgive me if I make a misstep... I am building a coil (22swg enameled copper wire, about 500 ft), some 4in inner diameter of the bobbin, 1" wide, will have ~ 450 ...
0
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1answer
136 views

Why do we use S-parameters for High frequency signals?

I have read at numerous places that S-parameters are used for analyzing systems which deal with high frequency. But why only high frequency? From what I have read, I have understood the following ...
1
vote
1answer
90 views

Line-out: why is there no impendance issue when plugging an amp rather than headphones?

Given that the input of an amplifier has very high impedance, while headphones have very low one, why can I plug either one or the other on the audio-out plug of my computer? Even with a degree on ...
4
votes
1answer
62 views

Calculating the current of an AC circuit

My goal is to calculate the current i(t) up in the right corner. Using the formula $$ Z_{total} = \left( U\over I\right), I = \left( U\over Z_{total}\right) $$ Given values are $$ R_{1} = 1k ...
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2answers
260 views

Multimeter input impedance and its effect on the measurement of charged capacitor's voltage?

while experimenting with capacitors, I charged a 15pF cap through a resistor to the voltage of a 1.5v battery. Then when I disconnected the capacitor and tried to measure its voltage with a 10Mohm ...
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votes
3answers
266 views

Electrical issue with USB ? Hi-speed device not working on own design

Disclaimer, I'm a SW guy, so please don't take anything for granted, and I would appreciate explanations in layman's terms :) We have a custom design based on ...
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2answers
94 views

Measuring Load Capacitance and resistance of 4~20mA transmitter

In order to make a spec sheet on a loop powered 4~20mA product, we need to measure the Device Capacitance and Device Resistance. Is there any standard procedure for measuring such parameters?