Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [noise-spectral-density]

Anything related to the noise spectral density, i.e. the function representing how the power of the noise signal is distributed among its frequency components.

Anything related to the noise spectral density, i.e. the function representing how the power of the noise signal is distributed among its frequency components.

See also Wikipedia on noise spectral density.

96 questions
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1/f noise, is it limited?

Basically my question is: I doubt noise density goes to infinity because we can reach the limit f→0 in any DC circuit in contrast to the limit f→∞ (which is an idealization because all circuit behaves as a low pass for enough f). If noise density…
user171780
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Antiresonance of multiple parallel decoupling capacitors: use same value or multiple values?

My quesiton: Is it better practice to put same-valued capacitors in parallel of capacitors of different values to decouple the high-frequency noise caused by digital ICs? Background Digital IC need a decoupling capacitor close to their supply pins…
andresgongora
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How to avoid Johnson noise in high input impedance amplifier

I don't have a circuit I'm working on, this is more of a theoretical question - I am trying to remedy a flaw in my understanding. Imagine I want to build a high input impedance amplifier to work in the low mV range, with a few nV/√Hz noise. I want…
Jack B
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What are the calculations to do in practice to estimate beforehand the noise seen on the output of this op amp circuit?

I would like help with understanding something better, but am not trained in electronics so please bear with me! I am trying to make a simple circuit to take a {-10V ... +10V} signal from a function generator, and to map it into the range {+1V ...…
teeeeee
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Noise Model for Zener Diodes

I am trying to design a noise source using discrete transistors and a Zener diode in the avalanche breakdown region. Therefore, I have several questions relating to the use of the diode... How does the quiescent current effect the noise…
Caleb Reister
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Accurately measure relative intensity noise (RIN) using RF spectral analyzer?

I'm trying to measure the relative intensity noise (RIN) of a laser using an RF spectrum analyser. It's a fairly common method (outline: How to measure relative intensity noise in lasers) although I wondered if someone more experienced might be able…
IanRoberts
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Help figuring out what is the limiting factor on the noise level in this analog optocoupler circuit

I am trying to build a circuit that takes a {-10V ... +10V} analog signal and outputs the same {-10V ... +10V} voltage but galvanically isolated from the input. The idea is similar to that of digital optocouplers, but for analog signals instead. My…
teeeeee
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What is the noise level as read on my oscilloscope?

The above is what I'm seeing on my oscilloscope. It's zener diode noise. Scope's set for 0.5V/div vertically, and 1ms/div horizontally. The oscilloscope has a 20MHz bandwidth, but the noise doesn't really change much at higher speeds. You…
Paul Uszak
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Why the noise from cascode transistors are negligible at low frequencies?

I am reading about noise of cascode amplifier in Razavi book, Design of Analog CMOS Integrated Circuits. However, I couldn't understand the yellow highlighted sentence below. Could anyone explain it? Why the noise from M3, M4, M5 and M6 are…
emnha
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Understanding Noise Figure of LNA (HP 461A amplifier)

I have recently got a HP 461A linear amplifier (from the 60's) which works from 1Khz to 150Mhz. I have checked that: it's input gives a SWR <1.1 across all spectrum (i.e., the input impedance is very close to the nominal 50ohm). The 40db Gain is…
makkiato
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Is noise a random process?

I have some confusion in noise signals and their nature. Can any one explain how the nature of noise signals is. Is noise a random process.
nbsrujan
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Why are there two sets of ENBW correction factors?

For calculating the equivalent noise bandwidth of a non-brickwall filter, I can find two different sets of numbers, both of which claim they are similar things: Order EqNBW 1 1.5708 2 1.1107 3 1.0472 4 1.0262 5 1.0166 6 1.0115 7 …
endolith
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How do you simulate resistor noise with LTSpice?

Is there a way to setup a resistor noise source (Johnson/Thermal noise)? I want to experiment with add a Johnson/Thermal noise source to a resistor for test in LTSpice, but not sure how to configure LTSpice to create a noisy resistor supply.
jsuarezbaron
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How to calculate expected RMS noise voltage out of digital audio system?

I have a PCB which includes an SOC with a built-in DAC that connects to an external active high-pass filter which then connects to a Class AB amp IC to drive an audio load. Using a spectrum analyzer, I measured the idle noise (20 Hz - 20 kHz…
zigzidane
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Measuring Noise Contribution of Amplifier in Antenna Amplifier System

I have a very simple setup that looks like the following: It is simply an antenna connected in series to an amplifier. The output of this setup goes to a spectrum analyzer where I measure some power (in some bandwidth). I am trying to figure out…
bgodfrey
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