Questions tagged [common-mode]
A common mode signal is a signal that is common (i.e. has the same magnitude and phase) to both inputs of an electrical device, as opposed to a differential mode signal. It is often desirable to reject common mode signals, in which case the common mode rejection ratio (CMRR) is an important metric.
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Common mode EFT protection with a transformer [closed]
I am using a transformer (VN38.13/13285) which is a surge protected and internally fused CE approved transformer. This transformer itself with a TVS diode after it doesn't prevent EFT Common Mode ...
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If the chassis is at high potential and a human touches it, will he get shocked? The proposed circuit is for the cancellation of CM current
This circuit is compensating the potential difference between the chassis and motor so the bearing current or leakage current cannot flow from motor to chassis to ground.
If the chassis is at a high ...
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3 phase 4 wire inverter output common mode choke selection
I designe and develope a stand alone 3 phase four wire inverter that it works with unbalanced output currents. The standard 3 phase 3 wire inverter output are used common mode choke like this (RB6132-...
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Common mode voltage concept in circuit analysis
I'm having trouble understanding common mode voltage and its application when analysing a circuit. Let's say I have an op-amp in the following configuration from Sedra's Microeletronics book:
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Input common mode voltage in differential amplifier used for high-side current sensing
I am confused about the input common mode voltage seen by an op amp configured as a differential amplifier for high side current sensing. Assuming that the op-amp and the load for sensing share the ...
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Input common-mode voltage range at different supply voltages
The OPA189 datasheet https://www.ti.com/lit/ds/symlink/opa4189.pdf?ts=1696944853447&ref_url=https%253A%252F%252Fwww.google.com%252F says on p.10 the input common-mode voltage range is between (V-)-...
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Differential Amplifier with unbalanced differential signal
The circuit topology of figure 1a corresponds to a differential amplifier with resistor load.
Since the signal generator available in lab does not have a differential output, a balanced
differential ...
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CMTI of a push pull converter
According to this article, a push converter has good immunity against Common Mode transient :
It is said "The flux generated by the current flowing in one primary coil cancels the flux generated ...
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Need of Cmfb in fully differential amplifiers
Instead of using cmfb circuit to set output dc common mode voltage Why can't we put at dc bais voltage at inverting or non inverting inputs of differential amplifier that way Vocm is set through ...
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Common-mode capacitance of operational amplifiers as defined in datasheet
The common-mode input capacitance is modeled as Ccm/2 on each operational amplifier input in https://www.allaboutcircuits.com/technical-articles/input-capacitance-analog-circuits-how-to-compensate-...
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How does INA 290 reduce voltage level from 120V to ICMR range of the corresponding op-amp?
How 120 V is in the Input Common Mode Range of the op-amps?
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Multiple 4-20mA Transmitters from Common Referenced Analogue Inputs
I'm trying to come up with a scheme for multiple loop powered 4-20mA transmitters controlled from seperate analogue voltages, which all have a common 0V reference. My inital thought was to use an ...
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Bias common mode and Impendence in relation to ASD1299
I was wondering if anyone would be able to help me understand the Bias common mode and Impendence in relation to ADS1299.
If someone has a ADS1299 for dummies that would be great
Thanks
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Effects of Improper Grounding on Common Mode Noise
In a DC power system like the one shown below in the diagram, a resistor is placed between the return wire and chassis to limit fault currents in the scenario where there is a high side to chassis ...
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Common mode voltage suppression for low side high bandwidth current sensing
I want to measure current of short duration high amplitude pulses using a low side shunt resistor. The test pulses are up to 400ns (2.5Mhz) with amplitude up to 3000V, depicted in the picture below.
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Why are the \$2R_{EE} \$ and \$r_o\$ in parallel?
Here is the BJT common mode and its half circuit in Microectronic Circuits.
The book says \$2R_{icm}=(1+\beta)(2R_{EE}||r_o)\$.
Why are the \$2R_{EE} \$ and \$r_o\$ in parallel?
I drew the T model of ...
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Frequency spectrum in PLECS for CM noise measurement
I am performing a simulation to measure the common mode noise in a buck converter. I have three models, an ideal buck, a non-ideal buck with parasitic capacitors, and a CM equivalent circuit to ...
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Path of common mode noise in a DC-DC converter
I have a doubt about the common mode noise propagation in DC-DC converters.
Consider a simple Buck converter,
the switching nose is where the potential difference between the varying voltage occurs ...
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Questions regarding ESD protection
I have a couple of questions regarding the Basics of ESD.
Usually, when we employ ESD protection, say placing a TVS diode on the signal line, the other end of the ESD diode terminal:
a) Will be ...
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Input common-mode offset voltage ranges of op-amp
I'm using an MCP6V81 op-amp.
While trying to understand, I see that the output of the op-amp can't be greater than Vdd and less than Vss. If that's the case, could someone clarify how the common-mode ...
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Ethernet RJ45 Mg Jacks - CMC placement
Ethernet RJ45 Mg Jacks. Some have common mode chokes on the PHY side and some have chokes on the cable side. What's the difference?
Some examples:
https://www.sparkfun.com/datasheets/Prototyping/...
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What exactly does "common-mode" mean in the context of op-amps?
I read this article about common-mode and rail-to-rail op-amps.
For the common-mode, does the op-amp need to be configured in feedback mode such as a non-inverting amplifier?
Should it be configured ...
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Common mode inductance without earth
Here is a schematic from TI:
I also attached a picture of the schematic part concerned:
I do not understand why there is a common mode inductance. (But I know that there is a reason :) I just do not ...
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Ground loop and oscilloscope isolated from earth
Here is an extract from this article
It seems that it is missing some words in the extract, causing me some difficulties to understand the beginning it makes the thing harder to me.
Why when the ...
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Using external DC input to remove DC component from signal using differential-amplifier based circuit
I want to use this Fully Differential Amplifier to design an OPAMP stage that is powered by +3.5 and -3.5 V DC power supplies, which will get a single-ended input signal that has AC and DC components.
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Does the orientation of the Ethernet magnetics matter?
I've this Ethernet magnetics transformer connected between the PHY and the Connector?
Does the orientation of the magnetics with respect to the PHY matter? Meaning, should the common mode choke inside ...
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What is a Fast-Stat Commonmaker actually doing?
Trying to get an Ecobee thermostat to work in my old house where I only have two wires going to my thermostat. Ecobee needs a common, and the remedy they suggest is a Fast-Stat Commonmaker, which has ...
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Common-mode gain of an instrumentation amplifier buffer stage
We discussed an instrumentation amplifier:
We were given the common-mode gain of the buffer pair (Op1 and Op2) for the common-mode output voltage \$\frac{1}{2}(U_{a+}+ U_{a-})\$ to be \$1+\frac{\...
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Wheatstone bridge with zero offset voltage
Can I power a Wheatstone bridge circuit with a positive voltage (say +5) on one side and negative (-5) on the other, such that the output common mode voltage is at 0V? I don't see any reason why not, ...
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How can I separate differential mode and common mode noise of measured noise spectra on the line and neutral?
The following spectra are the measured EMI conducted noise by a switchable LISN. As this LISN has only one BNC output, the noise separator can not be used. The following spectra are of the noise on ...
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Is a surge a common-mode signal or a differential mode signal?
When a power circuit is powered up, there is always a surge because there is often a big capacitor connected to the input to filter the noise.
Is the surge a commom-mode signal or a differential-mode ...
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I designed and built an op-amp using 4 NPN and 2 PNP BJTs. What are the pros and cons, and how can it be improved?
There have been some questions asked recently about op-amps, and I was curious to see how to make one with just NPN and PNP transistors. I did a simulation in LTspice and it seems to work pretty well, ...
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How to know whether a differential transceiver is internally terminated for common mode voltage or not?
In a keynote by Rick Hartly titled "What your Differential Pairs Wish You Knew", it is suggested that especially at high speeds, it is necessary to terminate the differential pair not with ...
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Can the DM inductors of an EMI filter be wound on the same core?
I want to implement the following EMI filter containing two separate LC filters such as DM and CM filters. Obviously, the CM inductors must be wound on the same core.
Can I also wind the DM inductors ...
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Common-mode choke with inputs shorted together
I came across this configuration in a schematic, and it makes no sense to me. I have to admit common-mode chokes are not my strong suit, but is this even going to act as an inductor?
simulate this ...
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What is exactly the common mode issue in this schematic?
I am taking the output of the shown differential amplifier to the microcontroller (1, 2 and 3).
Each opamp here is in a different PCB but all are being fed by the same supply (same ground) and the ...
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DM EMI filter components calculations
I'm attempting to design a passive DMEMI filter according to the paper titled "guideline for a simplified differential mode EMI filter design". Two formulas are presented in this paper to ...
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DM and CM EMI emissions measurement in LTspice
according to a youtube video V(SMA1,SMA2) is equal to 2DM_noise and V(SMA1)+v(SMA2) is equal to 2CM_noise. it is said that they must be divided by 2 and also multiplied by 1,000,000 to result in dBuV ...
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How to have a wider spectrum of FFT at LTspice?
I've used the FFT analysis tool to see the spectrum of DM and CM EMI noise in the range of 150K to 30MHz.
But the analysis stops at about 3MHz automatically and there is no option to set the max and ...
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Check 5V differential input with unknown common mode offset (comparator)
I want to output a +5V signal on my PCB when an external signal is 5V above its own ground level, but I don't know what the difference between the external and board ground might be (I hope "...
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How is the input offset voltage a function of common mode voltage?
I don't know about the internals of a opamps, but is it possible to explain how a change in common mode voltage changes input offset voltage Voff?
I'm asking because when the signal Vin is fed to the ...
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Why does this op amp input stage have single ended output?
Looking at the internal diagram of LM324:
I see that the output of the the input stage, which is a differential pair, is single ended rather than being a differential output.
How does then this input ...
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What is the standard common mode voltage of Media Dependent Interface MDI[0:3]± signals?
I am working on the selection RJ45 connector for MDI interface between PHY and the link-partner.
I am planning to use this PHY for my SGMII interface application. From various online readings, I ...
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What can this CAN bus like protocol be?
I am currently probing what seems to me the CAN bus twisted pair of my car. But the signals are not what I expect. One of the pair is like a typical CAN HI signal, however the idle state is a 0V and a ...
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How to simulate this circuit for common mode voltage effect?
Regarding my previous question and this paper, I wanted to simulate the circuit below to see whether it is rejecting common mode voltage as claimed. The paper says that sharing DAC's Vref with non-...
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Confusion with using non-inverting input to fix common mode voltage
Regarding this paper, and the following diagram:
We can see above that the non-inverting input of U2 is connected to Vref of the DAC. Signal input goes to the inverting input and Vref to the non-...
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EMI analysis for low power low voltage AC/DC
I've designed an 80W 220V-IN 400V-OUT PFC Boost converter in order to analyze its conductive EMI and design the proper active EMI filter for it. but as this is my first implementation project, working ...
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Common mode input voltage in a 4-20mA transmitter
I designed and built the following circuit
which is an almost straight-from-the-book 4-20mA loop transmitter. The idea would be to take an accelerometer axis (more or less 0.1 to 3.2V) and send out ...
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Paralleling common mode chokes
Regular chokes can certainly be used in parallel so that multiple smaller chokes with a lower current rating can be used. But does this also work for common mode chokes?
I would assume that ...
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Why feed a V_OCM outpin pin of a FDA?
The Analog Devices reference design CN0540 (see diagram below) shows an AD7768-1 ADC together with a fully-differential ADC driver ADA4945-1.
I am wondering why the common-mode voltage pin V_COM of ...
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