Electrical Engineering Stack Exchange
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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.

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. If your question deals with CMRR, consider tagging your question with both and .

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What is the common mode in common mode input voltage range?

The common mode voltage at the input of a difference amplifier is defined as $$\dfrac{V_1+V_2}{2}$$ and common mode input voltage range is the range of voltages at the input for which the opamp works as it's supposed to. But what is common mode…
Henk
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Why common-mode voltage is avarage of two input voltages in a differential amplifier?

I'm having hard time to understand the motivation behind the common mode voltage in differential amplifiers. I came to learn that common-mode voltage is chosen (v1+v2)/2 where v1 and v2 are input voltages of the differential amplifier with respect…
user16307
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What is the significance of Common Mode Signals?

I don't understand the physical significance of Common Mode Voltage. It is arbitrarily defined as the average of two voltages and is expected to be rejected by a differential amplifier. Why? What is its physical significance? EDIT my question was…
JGalt
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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 same current source as in the image. A colleague has…
Elektroneu
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Confusion about common-mode voltage in a single-ended system

I have trouble figuring out common-mode voltage related topics. I would like to illustrate my understanding first: The below op-amp has two inputs: V+ and V-, as usual. And lets say the differential voltage is: Vd(t) = (V+) - (V-) = sin(ωt) Let's…
user1245
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Understanding common "mode"

From my understanding of mathematics, the mode is the value that appears the most in a set of data. As such, how does this translate to "common mode" voltage? I understand how the cancelling out works, for example in instrumentation amplifiers (at…
upandouttherabbith0le
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How to interpret the CMRR at the data sheet of an amplifier?

Here is the data sheet of an AE101 amplifier http://www.hbm.com.pl/pdf/a0114.pdf At page 46 there is a line as such: Common mode rejection 0... 300 Hz dB >100 300 Hz dB >85 Do these mean for AE101 the common mode voltage will be…
user16307
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Common mode noise mitigation in two pin smps

How does a 2 pin (no earth ground connection) SMPS offer common mode protection? Is it safe to power appliances over it?
Jaacs Pottas
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Common mode range and DC common mode interference

Here is my basic understanding of common mode range for diff input amplifiers: As far as I understand the common mode voltage is nothing but the offset at which the diff signal is travelling above a common reference. And if this CM voltage exceeds…
floppy380
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Unclear common-mode voltage specs in the DMS-20LCD volt-panel-meter

I would like to buy a small digital volt-panel-meter. My eye fell on this series from Murata: DMS-20LCD (https://www.murata-ps.com/data/meters/20lcd.pdf) This meter can be powerd by either a 5V supply or 9V battery. The datasheet limits the Common…
K.Mulier
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Single-ended common mode gain

In the following circuit, what would be the single-ended \$A_{cm}\$? I realise that there would be no current through \$R_e\$ in common mode and that this is a CE (Common Emitter). However, I am not sure whether the single-ended \$A_{cm}\$ should…
peripatein
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A question about coupling differential signals safely and Input Common Mode Voltage Range

This may sound a weird question but couldnt resist to ask here. Lets say I have a differential signalling mode floating battery powered transducer(where the outputs are mirrored) and the differential voltage across its outputs Vd at a moment is 1V.…
user1245
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Direction of common mode current

I am looking at this circuit: (taken from here) In the schematic, the common mode current does not enter into the load - it is bypassed to ground through the parasitic capacitance. I have couple of doubts: How does this capacitance allow common…
Mohammed Azlum
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