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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Current Rating in Common Mode Choke

What is the meaning of this current rating which says "unbalanced" current? I know in common mode chokes the common mode current rating is given. Why here it is written as Iunbal.?
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How are SPICE files created compared to S4P files generated from a VNA?

When measuring impedance versus frequency using the same data in both SPICE and S4P formats, why do I obtain different results? COMMON MODE IMPEDANCE Common mode impedance 10514 Ohm at 79.1 MHz S4P ...
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Why is the core resistance modeled as 2*Rp and capacitance as Cp/2 in a common-mode choke?

I directed my attention to a paper regarding the modeling of common-mode chokes. Within this paper, the authors structured the circuit in such a manner that they designated the core resistance (...
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How is the boundary of input CM level calculated?

I will briefly state my understanding of the following equation, and then pose three questions at the end. Equation (1) (2) refers to the circuit in the first picture, Equation (3)(4)(5) refers to the ...
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Why will the offset of a source-follower which is connected to the output of an opamp as a voltage buffer limit the op-amp output swing?

I am currently reading chapter 12, "The Common-mode Feedback Circuit" in Analysis and Design of Analog Integrated Circuits by Gray and Hurst. Page 815, gives the following statement for ...
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Testing input common-mode voltage range of an op-amp

I have been trying to develop a set-up that could test the input voltage range and output swing of an op-amp. To measure the input voltage range, the output should swing within the limitations ...
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CM filter of differential input(AD7383-4)

I'm trying to make a 3-phase inverter using AD7383-4 for converting analog current signal to digital. Typical application of AD7383 which is given by datasheet. AD7383 gets pseudo-differential input ...
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How to write \$V_{\text{a0}}\$, \$V_{\text{ab}}\$ and \$V_{\text{cm}}\$ for the three-phase three-level inverter in terms of the switching signals?

How to write \$V_{\text{a0}}\$, \$V_{\text{ab}}\$ and \$V_{\text{cm}}\$ for the three-phase three-level inverter in terms of the switching signals? For the three-phase two-level inverter, the values ...
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Common mode voltage with configurations of Opamp

I am reading this article (https://www.analog.com/media/en/training-seminars/design-handbooks/designers-guide-instrument-amps-complete.pdf) in order to understand more how traditional instrumentation ...
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Add common mode noise into existing circuit

I have a complex 24 VDC in circuit that I need to demonstrate fault cases as a result of potential common mode noise due to a floating earth on the PCB. As such, I am interested in the best way to ...
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Radiated Emissions problem

This is regarding some Radiated Emissions testing unintentional radiator. We did a pre-scan of our product and we got the following EMI signature. Critical frequency is at 314.986 MHz Polarization is ...
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Input common-mode range vs output voltage (INA826) interpretation

I'm starting a new design using INA826 and analyzing the input common mode limitation, I do not understand the differences between this curves; I mean, why in figures 11 and 12, gain and VS is not ...
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Transfer Function of Differential opamp with common mode voltage

When we consider the relationship between Vout and Vin of the differential amplifier, we connect one of its inputs each time to the ground to ignore that input voltage in the calculation, in order to ...
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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 ...
Awaisha memon's user avatar
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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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Difference between current and voltage expressions in fully differential circuits

This is an old, unimportant question. I am adding a bounty on it to effectively raise the bounty of the question linked below. Please answer the linked question for the bounty. Both bounties will be ...
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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{\...
Ondry's user avatar
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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 ...
Anas Malas's user avatar
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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 ...
Elektroneu's user avatar
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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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