It defines the Voltage/Current characteristic of any dipole circuit
1
vote
2answers
68 views
Custom USB Impedance question
I'm looking at making my own USB cable for a project. The primary issue I'm having is that I'm getting a lot of capacitance in my cable between D+ and D- (400ish pF) which is enough to throw off the ...
-1
votes
0answers
35 views
Problem with impedance matching on DIY 4 pole 3.5mm audio splitter
I built an audio 4 connector 3.5mm splitter. The goal is to play a sound clip through a phone's mic input across a call, while recording the same sound clip on the computer. I used the TRRS ...
0
votes
2answers
57 views
How does less cable impedance, source/termination impedance, lead to longer cable length for higher data rates?
This question is about high speed digital transmission on a transmission line,
I need to know about how does the
(1) impedance of the transmission line and the
(2) source impedance and
(3) ...
4
votes
2answers
152 views
Why Characteristic Impedance must be “50” ohms?
Where does this number came from?
For single ended it must be 50 ohm and for differential pairs 100 ohm. Why?
For PCB with controlled-impedance these are that common numbers. Outside of the PCB you ...
3
votes
1answer
77 views
Solving for RC circuit transfer function
How do I calculate the transfer function of this circuit? \$H(s) = \dfrac{V_o}{V_i}\$
I apply the Kirchhoff's law at the node \$V_x\$ but I still have \$V_x\$ as unknown :
\$\dfrac{V_x - ...
2
votes
2answers
40 views
Input impedance of Arduino Uno analog pins?
I'm using the ACS712 hall-effect based current sensing chip on some small robotic arm motors, and reading in the analog voltage with an Arduino Uno. I've had reasonably good results, but only after ...
2
votes
2answers
137 views
How does a real current source change its pd to keep constant current
An ideal current source is able to change its potential difference at the output to keep the same current at the output regardless of the load imepedance there. Real current sources are able to do ...
5
votes
2answers
165 views
High to low impedance microphone
I'm a helicopter pilot. I'm thinking of buying a headset Bose A20. My problem is that the Bose headset comes with a high impedance microphone, but the helicopter I'm operating is using a low impedance ...
0
votes
3answers
172 views
Input impedance is higher in Common-Emitter than Common-Base?
Why is input impedance is higher in Common-Emitter configuration as compared to Common-Base configuration as signal is applied on Base-Emitter junction in both Amplifiers. Not in both configurations ...
3
votes
2answers
239 views
Input and Output Impedance of a BJT
Hi I'm new to electronics and I would like to know how to measure experimentally the input and output resistance of the following common emitter configuration. I have access to a voltmeter, signal ...
0
votes
2answers
119 views
Electron flow due to impedance?
In the basic electronics lecture today not only I but whole class became confused by an explanation of our teacher that in high impedance value electrons movement become easier while in low impedance ...
1
vote
4answers
154 views
Headphones impedance and the SPL
The headphones A has an impedance of 32 Ohms.
The headphones B has an impedance of 250 Ohms.
Both of the headphones are similar by size.
Is it right that the headphones B will play quieter by ...
6
votes
1answer
90 views
How can SCRs be effectively paralleled?
I'm designing a precharge circuit which will carry 200A when closed. I'd like to use MCO150 Silicon Controlled Rectifiers, but they won't handle the current. Two in parallel looks like the most ...
5
votes
1answer
156 views
What is the Thévenin equivalent of the mains power supply?
Thévenin's theorem says that any voltage source can be modeled as an ideal source in series with some complex impedance. How does one quantify this model for AC mains supplies? What parameters are ...
0
votes
1answer
88 views
Can someone explain impedance in simplest way? [duplicate]
I know in DC it is Resistance of the load.
In AC is it impedance of a line correct? can someone please help me understand impedance and types of impedance.
Zero Sequence, Positive sequence and 2 ...
0
votes
2answers
153 views
Antenna analyzer
I want to measure the impedance of an antenna (at 434MHz) and for learning/fun try to build a circuit to do so.
I found the return loss bridge
http://www.vk2zay.net/article/179
Can I measure a ...
6
votes
4answers
461 views
How to achieve high impedance input on OPAMP without sacrificing bandwidth
I was trying to simulate (In LTSPICE) buffer for ADC 08200 that would have 1Meg input impedance it is about to be used with standart oscilloscope probes. But I am having problem with bandwidth ...
4
votes
2answers
250 views
How does the conversion between admittance and impedance affect phase angle?
Wikipedia tells me that admittance \$Y\$ is the reciprocal of impedance \$Z\$:
\$ Y = Z^{-1} = \dfrac{1}{R+jX}\$
which makes plain enough sense to me, except that I've forgotten how complex numbers ...
2
votes
1answer
140 views
Huge variation of impedance calculators with same parameters?
There are many free (e.g. AppCad from Agilent) microstrip impedance calculators on the web. I've tested now several, because the first two did show a huge difference in the calculated impedance for a ...
0
votes
1answer
94 views
What is a good tolerance for impedance matching or how to calculate losses?
If you build a microstrip on a silcon wafer, connected by picoprobes via SMA connector and cables to a VNA, what is actually a good match of the impedances of the cables and the waveguide. Is there a ...
1
vote
1answer
52 views
Point of thin SiO2 layer for surface microstrip?
Reading some scientific journals I saw that research groups often use a silicon wafer with appropriate dielectric constant/relative permittivity and then build a microstrip (coplanar SGS or edge ...
3
votes
2answers
171 views
Square wave generator has nigh-useless output
I have a system that was designed for testing digital components. I have a device in the system which is used for generation and acquisition of digital signals. Now, I will happily admit to not ...
5
votes
2answers
193 views
Input impedance of inverting amplifier clarification
Take a standard inverting amplifier:
I'm unclear on what the input impedance is. At first I thought it was the equivalent resistance from the inverting input to the ground, which would be Rin || Rf, ...
3
votes
1answer
151 views
How does the addition of a bias-t circuit affect the impedance of a transmission line?
I've got a GPS circuit where the antenna is connected directly to the GPS receiver via a coplanar waveguide designed for an impedance of 50ohms. Unfortunately, I neglected to add the bias-t circuit ...
3
votes
2answers
97 views
Under what circumstances can impedances be simplified to simple resistances?
Consider the following circuit:
This is a simple first-order low-pass RC filter. The cutoff frequency is:
\$ f_c = \dfrac{1}{2 \pi (1k\Omega) (1\mu F)} \approx 159 Hz \$
The reactance of C1 at ...
3
votes
2answers
354 views
adding a yagi antenna to a bluetooth dongle
I want to set up a Bluetooth link between devices that are over 2000 feet apart. Yagi antennas for 2.4GHz that can connect to routers are available. A cheap Bluetooth dongle that can be easily taken ...
4
votes
1answer
313 views
Why are loudspeakers manufactured in various impedance values?
I'm acquainted with the concept of impedance matching in audio applications, but there's something that eludes me. First, a snippet from a home theater site:
Loudspeakers have impedances of 8 ...
2
votes
1answer
92 views
Verilog proper use of high impedance value?
In verilog, what are some examples of when one should opt to use the high impedance value Z?
Thanks
2
votes
4answers
804 views
How to specify 100 ohm impedance on a pcb gerber
I've been using Altium for several years when I've needed to designed boards. However it's all been for simple analog designs and never anything too technical. I'm now trying to take a jump into a ...
3
votes
2answers
405 views
How to find the output and input impedance of an amplifier
For example:
Vcc -> GND
capacitors -> wires
NPNs -> hi and current source
The schematic above becomes:
How can you find the output and the input impedance?
The answer in this case should ...
2
votes
1answer
167 views
Circuit review: Impedance bridging for microphones
I have a pair of specialist condenser mics with a nominal output impedance of 3.6k Ohm that I would like to interface with mic preamps with nominal input impedance of 2.2k Ohm. Does this impedance ...
2
votes
2answers
196 views
The “10x rule” for impedance bridging
Quoting the Wikipedia impedance bridging article . . .
A connection is commonly said to be bridged if the load impedance is
at least ten times the source impedance.
Why the magical numer 10?
...
2
votes
1answer
700 views
Mic preamp: Inverting or non-inverting op-amp configuration?
What are the relative merits of using inverting/non-inverting op-amp configurations for a microphone preamp? While searching for microphone preamp schematics based on op-amps, I have found both ...
1
vote
3answers
279 views
How do you determine the input impedance for an inverting amplifier?
Essentially I am getting confused trying to do the sums for an op amp with a gain of 10dB and an input impedance of 1kohm.
I worked out that \$\frac{V_{out}}{V_{in}}=-\frac{R_{2}}{R_{1}}\$ because ...
0
votes
0answers
167 views
Which op amp for microphone voltage follower?
I have been modifying a 4-channel digital field recorder to use specialist condenser microphones. I have got all the phantom power issues sorted and am able to make recordings. Channels 3 and 4 were ...
0
votes
1answer
150 views
SPI interface is working, but there is no power, what could be wrong?
I have an ADC attached to my uC on a custom PCB. The traces are just directly connected between the uC and the ADC. Here is a photo of an oscilloscope trace of SCK and MISO. SCK is Blue, MISO is Red. ...
0
votes
1answer
134 views
Exam question: measure amplifier \$h_{oe}\$ using a signal generator and oscilloscope
I'm running through some old exam papers at the moment and one of the questions are:
The parameter \$h_{oe}\$ is needed to calculate the output impedance of an amplifier. Explain in detail how to ...
0
votes
1answer
173 views
How to go about designing an impedance matching circuit for microphones
I have a black-box circuit attached to a condenser microphone. I would like to replace this condenser microphone with another. I have output impedance data for both microphones across frequency. The ...
4
votes
3answers
576 views
How to build impedance meter
I want to build impedance meter for measuring input-output impedances of audio amp stages.
Does anyone have experiences with such projects. I want to measure stages while running (hot measuring) so ...
0
votes
1answer
209 views
Testing a 0.3W, 8ohm speaker?
I have a 0.3W (RMS), .8ohm speaker coil + cone that I want to test using various music. However, the 8ohm impedance is lower than typical earbuds (24ohm), and also I can't find headphone jack power ...
2
votes
1answer
223 views
How to measure microphone output impedance
Is there a method to measure the output impedance of a condenser microphone?
2
votes
2answers
107 views
individual ethernet cable wire uses
I'm going to use ethernet cable as a long range cable for serial (5v) and power (5V and 16V, almost no A) and I remember reading that because of the loops in the wire and the impedance effect some ...
-1
votes
1answer
82 views
Impedance waveform
How to get a good picture of fft of Impedance with voltage and current signals ? ( How to deal with zero crossings of current as impedance is taken as (V/I) ?
1
vote
1answer
143 views
Output Impedance of a Digital Output
In High-Speed Digital Design, Dr. Johnson illustrates an example of calculating the output impedance of an IC (page 48.). He uses VOL of 0.15 V and VOH of 4.32 V (@ Vcc = 4.5 V) with an Io of 4 mA to ...
1
vote
1answer
218 views
How to mix High-Z and Low-Z audio signals? (Sum should be High-Z)
I'm trying to inject additional sound into a phone call. Therefore i modified a basic cable headset to use audio from my iPod.
This is my current prototype circuit:
That circuit is already ...
10
votes
2answers
3k views
Constant current, constant power and constant impedance loads
Ive been looking for information on constant power, constant current and constant impedance/resistance loads, there's some information about the constant current loads, but very little that really ...
2
votes
1answer
1k views
Electronic aspects of iPhone 3.5mm audio output
I am working for a while now on a small project of building an external mic for the iPhone to be hooked in parallel to headphones (via the 3.5 mm jack). Basically, I want to replace the iPhone's ...
1
vote
1answer
309 views
Interface telephone handset
I have an immediate need (for a stage play) to take the audio from the microphone of a telephone handset and feed it to a Shure M67 audio mixer, familiar to anyone who's been in radio for a while ...
8
votes
2answers
516 views
Is this resistor needed in this opamp circuit?
I'm looking at the datasheet of the MCP6241. There's this schematic:
The op-amp has a input bias current of 1 pA, and \$ 10^{ 13}\Omega\$ input impedance. Is resistor Rz still needed then?
5
votes
2answers
1k views
Impedance Matching Differential Signals
I'm designing a circuit with RFICs using differential signaling. I'd like to keep noise to an absolute minimum. Let's use the mixer (LT5560) as an example. All of the reference schematics match to 50 ...
