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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.

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A-Weighted Noise Power Calculation

Can anyone please show me how to calculate the A-weighted noise power of a noise source. Consider the case of a resistor having a spectral density of 4kTR. What is the A-weighted noise power of this ...
Kenlucius's user avatar
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Noise Fluctuation with MAX40660

I am currently implementing MAX40660 as a high speed TIA amplifier. In the process of testing the basic functionality of the circuit, I have implemented a pcb design similar to the evaluation kit. ...
exatec's user avatar
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Noise density in 1/f region

The datasheet of the ADR1000 voltage reference specifies the 1/f noise density as 30nV/sqrt(Hz) at 10Hz and 300nV/sqrt(Hz) at 0.1Hz. Given that this is the 1/f region of the voltage reference, how can ...
Stefan Wyss's user avatar
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Noises are measured over a bandwidth. Is 50Hz and 900Hz noise the same at 1kHz bandwidth? [closed]

They say noise is over a bandwidth. At a bandwidth of 1000Hz. Is the noise at 50Hz and 900Hz similar? If yes. Please made a quick drawing how the noise at 50Hz and 900Hz look like roughly so I can ...
Jtl's user avatar
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Why different noise terms are read at specific sampling interval in Allan Variance plot?

I was trying to identify Quantization Noise, Angle Random Walk, Bias Instability, and Rate Random Walk from Allan Variance plot which as Allan deviation on y axis and Sampling Time Interval ...
Mahesha999's user avatar
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65 views

Impact of laser current source noise on RIN (relative intensity noise)

I am trying to specify the noise requirements for a constant-current source that would drive a diode laser with a certain relative intensity noise PSD. Lasers typically behave as forward-biased ...
chrisp's user avatar
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3 votes
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138 views

How to properly compute noise power spectral density?

I am confused about two different definitions of Power Spectral Density (PSD) that I have seen online. The first comes from the National Instruments LabVIEW documentation (1): $$ PSD = \frac{PS}{\...
Nick's user avatar
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Simulating Gyroscope with ARW, BI, and Spectral Density Using Physical IMU Data

I'm currently working on a state estimation project that relies on IMU data. While I have access to a physical IMU, I'd like to simulate gyroscope data with specific parameters, including Angle Random ...
user3106378's user avatar
2 votes
1 answer
235 views

Noise Figure in LTSpice

I'm simulating an LNA from a paper. It's using HBT BiCMOS technology an one of the things the paper shows is the simulation of NF in range of 3GHz to 10GHz. I'm trying to replicate the simulation with ...
JOAQUÍN PIÑEIRO's user avatar
1 vote
2 answers
236 views

Noise scaling in a current source

I have a bunch of constant current sources in my lab: some are laser diode drivers and some are DC power supply units that have a constant current mode. I've known from prior experience that some of ...
optnon's user avatar
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2 votes
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Low noise virtual ground, voltage reference or LDO + op amp?

I'm doing some sensitive signal measurements in 1~10kHz range where I amplify and filter (multiple active stages) a small voltage signal by hundreds ~ thousands of times and then sample it. A negative,...
Wjx's user avatar
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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 ...
jsuarezbaron's user avatar
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117 views

Random telegraphic noise and Lorentzian noise power spectral density

Following the example of the Lorentzian noise power spectral density shown above (ref), I would like to clarify the following: In the first figure (labeled by (c)), May I please know why the constant ...
Greta's user avatar
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1 answer
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Understanding the discrepancy between the input impedance of a signal analyzer and the input noise

The manual of a signal analyzer I am working with states that the input impedance is \$ 1 \ {\rm{M\Omega}} + 50 \ {\rm{pF}} \$, the manual also states that the input noise is \$< 10 \ {\rm{nV_{rms}/...
user27119's user avatar
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Input noise of ADC AD7768 with opamp driver ADA4945-1

I'm operating an ADC AD7768 with an opamp driver ADA4945-1. I measured the noise for three different cases: Both differential inputs open/floating Both differential inputs connected to AGND Both ...
Charly's user avatar
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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, ...
zigzidane's user avatar
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Can an LNA noise figure be normalized to dBm to estimate the minimum detectable signal?

If a device claims a noise figure of 0.3 dB NF such as the Qorvo QPL9547, can you calculate the dBm value of a signal that is at the noise floor (ie, a barely detectable signal)? Otherwise stated: I ...
KJ7LNW's user avatar
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How to calculate the phase noise contribution of an active loop filter in PLL

I want to calculate the contribution of each phase-locked loop (PLL) module to the total phase noise that has been done in ADIsimPLL. I'm having trouble calculating the contribution of the loop filter ...
shang xu's user avatar
3 votes
1 answer
806 views

Spectrum of Mains Power Line Noise -- Peculiar Frequencies

I am trying to understand the noise induced in wires running adjacent to a mains power line. For that purpose, I took about 4 meters of extension cord and 4 meters of RG6 coax and tied them next to ...
Math Keeps Me Busy's user avatar
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0 answers
299 views

What determines noise spectral density of diode-resistors?

One common way to think of a diode is that it is a variable resistor, whose resistance depends on its voltage drop and can be controlled via its bias current. I have two questions about how far this ...
tobalt's user avatar
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How to reconcile units in accelerometer noise density

I am trying to model an accelerometer in MATLAB. It is asking for the noise density in (m/s^2)/sqrt(Hz). The datasheet for the IMU I am trying to model gives output noise in (m/s) for the 100Hz ...
Jonathan Taylor's user avatar
1 vote
1 answer
254 views

Voltage RMS and Voltage Spectral Density from ADC Sample are Not Consistent

I have time series data from a 100 MS/s ADC, and I would like to calculate the RMS noise and the voltage spectral density (VSD), and see consistency between the two. I'm using a 16-bit ADC, and the ...
Dan's user avatar
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2 answers
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Noise figure to voltage noise spectral density hand calculation

The RF LNA of interest is the PGA-105+ from mini-circuits. From only the gain and noise figure I calculated the voltage noise spectral density that would be present at the amplifier input. If anyone ...
Max W's user avatar
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Effect of Antenna and gain on PSD of a radio receiver

I have a cheap SDR receiver and today I was trying to measure the noise in the system. I tried to disconnect the antenna and measure the power over the frequency range of the device. I also decided to ...
edmeme's user avatar
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2 votes
1 answer
175 views

Why does current noise flow through the parallel combination of R1 and RF in a non-inverting opamp?

I am following this reference for noise calculations of a non-inverting op-amp. I am not able to understand why the equivalent resistor is the parallel combination of R1 and RF as shown below: I ...
needbrainscratched's user avatar
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46 views

What does it mean when the output of an auto co-rrelation function is the unit impulse at t=0?

I read that auto-correlation function of white noise is unit impulse at t=0 is of strength N0/2. What does it mean that it is a unit impulse at t=0 ?
Circuit_Breaker0.7's user avatar
2 votes
2 answers
593 views

Amplitude Spectral Density from a Fast Fourier Transformation

I want to calculate the Noise-equivalent Power (NEP) of a photodetector. Hereto, I have to measure the Amplitude Spectral Density (ASD) of the detector and divide the result by the Responsivity: The ...
Alberto's user avatar
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1 answer
299 views

Noise equivalent power of thermopile sensor?

I am working on the characterisation of thermopile sensor and stuck in determining the NEP of the sensor. My thermopile sensor with AD8630 amplifier receives IR radiation coming from the blackbody at ...
Pukhtun's user avatar
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1 answer
169 views

OP amp noise density and Johnson noise (Thermal noise) for 16bits ADC

I am trying to create a analogique amplification chain between a piezo sensor (10mVPP) and 16 bits ADC in 3V3 range. I try to simulate the chain on LTSpice to get the lower noise density I can get. @...
rom1nux's user avatar
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1 answer
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How does Ohm disappear in noise/power spectral density unit?

Power spectral density is commonly expressed in Watts per Hertz (\$W \over Hz\$) or \$V \over \sqrt{Hz}\$. When I try to derive these for a resistor I get confused on the units. If we define noise ...
user1999's user avatar
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5 votes
2 answers
979 views

What causes flicker or 1/f noise?

What physical processes causes the generation of electrical and radio/EM/RF flicker or 1/f noise? Or why are those sources not generating normally distributed electrical observables (such as thermal ...
hotpaw2's user avatar
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1 vote
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104 views

RC noise figure calculation

I would ask for some help with noise figure calculation for circuit attached. It is front end of improvised differential probe that I would like to build. I am aware that simulators such as LTSpice ...
Wintermute's user avatar
5 votes
1 answer
286 views

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 ...
makkiato's user avatar
4 votes
0 answers
62 views

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 (...
bgodfrey's user avatar
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2 answers
129 views

What is the math behind high FM frequency components being more noise prone? [closed]

what is the math behind the phenomena that higher frequencies are more prone to noise? The use of pre-emphasis to boost the higher frequency components to get a better S/N ratio. Can you provide ...
Joe's user avatar
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1 vote
1 answer
403 views

Is noise density over a bandwidth a measure of the noise's standard deviation?

Suppose I have a sensor which has a dominant white gaussian noise source, a \$1\textit{unit}/\sqrt{Hz}\$ noise density and a bandwidth of 100Hz. Then the noise becomes 10\$units\$. Is this a measure ...
john morrison's user avatar
6 votes
2 answers
875 views

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 ...
teeeeee's user avatar
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2 votes
2 answers
332 views

What noise frequencies is an oversampling ADC susceptible to?

When calculating the input-referred noise and filtering to a 24-bit sigma-delta ADC (MCP3561), I hit a roadblock. Knowing the noise spectrum density (nV/sqrt(Hz)) of a signal noise source, like ...
Anders Petersson's user avatar
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0 answers
71 views

Simulation of the injected noise to oscillator in Virtuoso

I have a differential LNA that injects current to an oscillator. I want to see the thermal noise injected to the oscillator. This noise is composed of the noise of oscillator + noise of the LNA. Now ...
Fateme's user avatar
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10 votes
3 answers
1k views

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 ...
teeeeee's user avatar
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3 votes
0 answers
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Total thermal noise of a photodetector connected to a spectrum analyzer

I connected a photodetector to a spectrum analyzer (SA) and observed the signal (i.e. noise) on the SA when there is no light hitting the detector. I noticed that when I set a low spectral resolution ...
Flav's user avatar
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Power spectral density on the output of frequency modulator?

Is there a formula with which we would be able to calculate the power spectral density on the output of a frequency modulator? The information we know is that we have a receiver working in 180MHz ...
user avatar
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2 answers
632 views

Can we use both FFT and PSD to obtain a random signal's frequency domain representation?

I always encounter random noise frequency domain representation as PSD(not FFT), something like in the below plot: Without diving into math too much, practically speaking can we always use FFT ...
GNZ's user avatar
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1 vote
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Phase noise of a digital PLL

I assume the reader is aware of how a DPLL works. The DPLL oscillates with a frequency of \$F_{out}\$. The DCO free running frequency is \$F_{free}\$. In the model of our DPLL we've only considered ...
dirac16's user avatar
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200 views

How does one calculate output voltage noise of a current output DAC?

I am using a current output DAC connected to a voltage reference and a transimpedance amplifier. I know the noise characteristics of the voltage reference and the amplifier. The DAC simply lists "13 ...
justinis's user avatar
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0 answers
131 views

Does the profile of phase-noise power spectrum density (PSD) vary with time?

I will promptly provide any detail or revise my question aimed at any feedback. Does the profile of phase-noise power spectrum density (PSD) vary with time? The conclusion may be that it won’t ...
wu yi's user avatar
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2 votes
3 answers
828 views

Johnson-Nyquist noise for a lossy inductor?

In searching the internet for thermal noise on an inductor and I'm not finding much on the basics for a real lossy inductor. I'm interested in thermal noise for a fixed inductor in a surface mount ...
acker9's user avatar
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2 answers
102 views

The mean value of phase noise as a stochastic process

What is the mean value of phase noise as a stochastic process? Where can I get a theoretical analysis of this topic?
wu yi's user avatar
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3 votes
0 answers
111 views

Noises of switching power supply

I made a switching power supply (input: 24VDC, output: +-15Vdc) for LEM (current sensor). Noises of the power supply caused the output of LEM to become a bad waveform, but I don't know how to ...
John's user avatar
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1 vote
1 answer
359 views

Maximum Allowable Noise of ADC Input Signal

I have a question about calculating the maximum allowable noise for an ADC signal conditioning stage. I have an existing signal conditioning stage as well as an ADC on a microcontroller. I would ...
Matt's user avatar
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