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.
335 questions
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Common mode signal definition: why use the arithmetic average of the two signals? Is it empirically motivated?
In a post I made the other day about common mode signal and op-amps, some exchange in the comments led me to note that the definition of \$V_{\text{CM}}\$ seemed rather arbitrary. The canonical ...
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1 answer
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Differential amplifier common-mode gain
How do you find the common-mode gain of this circuit? \$\lambda > 0\$, and \$g_mr_o \gg 1\$. Using \$A_v=-G_mR_\text{out}\$.
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Input common mode for a switched capacitor integrator
I had a question about finding the input common mode of a differential switched capacitor integrator (shown in the figure below). The integrator is a conventional delaying integrator with two non-...
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5 votes
3 answers
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Understanding differential buses: characteristic line impedance
Lately, I've been studying filters and differential buses, and there's still one detail that doesn't fully make sense to me — it's related to the line impedance and how it may affect the calculations. ...
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1 answer
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Why does ATM90E32AS require GND connection despite differential inputs?
I’m working on a test setup using the ATM90E32AS energy metering IC. As an analog signal source, I’m using an AD9833 waveform generator connected to an Arduino. I generate a 50 Hz sine wave from the ...
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3 answers
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Why does an op-amp's common-mode input voltage range not shrink with higher open-loop gain?
I'm trying to understand the relationship between an op-amp’s open-loop gain and its input common-mode voltage range. Let’s say I’m working with an op-amp that has a power supply of 2V and an open-...
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1 vote
3 answers
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Transfer Function of multiple feedback bandpass filter (with Vcm at positive terminal)
How to calc bpf 1 transfer function? all questions I see on net have gnd at non-inv term. but here it is Vcm because of which constant term coming. how to get Vo/Vi?
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2 answers
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Do cascaded common mode chokes add to each other?
Will cascaded common mode chokes give an impedance which is the sum of their individual impedances over their respective frequency ranges? By this, I mean if we graphed the CM impedance of multiple CM ...
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