It defines the Voltage/Current characteristic of any dipole circuit
7
votes
1answer
97 views
Impedance of differential inputs on AD converters
I'm currently trying to attach a rather fast ADC/DAC-converter chip to an FPGA to receive and transmit RF in the future, but getting the converter to run and attaching a signal generator and an ...
3
votes
4answers
133 views
Component with an impedance that has a negative real part
Is there an electrical component such that its impedance has a negative real part ?
Fact: Any electrical component made from resistors, inductances, capacitors (connected in possibly complex ways ...
2
votes
1answer
65 views
Is it possible to derive complex impedance (magnitude + phase) from VNA 1-port network?
With the scattering parameters of a 2 port network I can measure reflection and transmission by a network analyzer and calculate complex impedance, via S-parameters.
Now I've heard (no source) that ...
1
vote
0answers
44 views
What does the impedance look like around a small resonant loop?
Say I have a hoop of conductor, broken at the top, with a capacitor across the gap. The inductance of the hoop and the capacitance form a series resonant LC circuit:
Now, say this loop is excited ...
2
votes
2answers
136 views
Can motherboard heatsink screws change the inductance of nearby traces?
I have bought motherboard and heat sink. The heat sink uses metal screws and the screw heads are isolated from the board with thin mica insulators. But the screws end up being above some traces on the ...
1
vote
2answers
69 views
Powering two 8-Ohm speakers in parallel with a 4-Ohm per channel audio amplifier
Are there any possible problems powering two 8-Ohm speakers in parallel with an audio amplifier designed to drive 4-Ohm per channel? (Both the speakers and amplifier are generic, and the speakers are ...
-1
votes
1answer
65 views
Write the mesh equations for this network.,
I am still new with this program so I am not sure how or if it is possible to set the inductor and capacitor to there impedance values. I know in multisim and in icircuit it isn't possible to set ...
2
votes
1answer
45 views
Estimated impedance of a 12V bleeper?
The bleeper(buzzer) I am using is rated for 12 volts DC. It is a piezo electric bleeper and the frequency is created by an internal oscillator.
I am not aware with the functioning of peizo electric ...
1
vote
1answer
58 views
Impedance between BJT base and ground of a common emitter amplifier circuit
What is the impedance between the base of the BJT and ground of the common emitter amplifier circuit? The answer should be in terms of RE and hfe (the small current gain of the transistor). Is this a ...
3
votes
2answers
74 views
Understanding why use Laplace transforms for circuits
I am an Electrical Engineering student and in my Circuits class, I learned that using Laplace transforms is helpful while analyzing circuits. I see how it makes our calculations easier but I still ...
3
votes
2answers
143 views
Reactance / Inductance / Impedance of a 1:1 Transformer
I've searched around and poored through what references I have available, and haven't been able to find an answer to this question.
Regarding 1:1 transformers, I found a website where an audio ...
1
vote
1answer
44 views
Charge indicator LED
I'm designing a battery charger PCB using a LTM8062 2A battery charger IC. I'm going to use it to charge a 14.4v battery and I would like to have an indicator LED to let you know when it's done ...
-6
votes
1answer
50 views
Voltage/resistors/series/impedance/meter
Assume you measure a power supply voltage through a series 1M OHM resistor and observe that is drops by 1/2 its former value when no resistor is in series. What is the input impedance of the meter? ...
1
vote
3answers
106 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 ...
0
votes
0answers
96 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
72 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
185 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
92 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
128 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
160 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
193 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
202 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
277 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
121 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
169 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
91 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
166 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
92 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
166 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
558 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
367 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
162 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
107 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
53 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
175 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
262 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
165 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
98 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
407 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
329 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
95 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
933 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
448 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
174 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
210 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
740 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
304 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
174 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
144 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 ...
