# Questions tagged [noise]

About issues caused by electrical noise, or improving the Signal/Noise ratio of an analog circuit.

215 questions with no upvoted or accepted answers
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254 views

### White and Pink Noise Generator Circuit - Cryptic AC Analysis

The “Electronic Devices and Circuit Theory” book (by Boylestad, Nashelsky) gives a brief description of a random noise generator circuit at the end of “BJT AC Analysis” chapter. (Btw, exactly the same ...
84 views

### How to generate different noise in LTspice from run to run

I'm trying to simulate noise in my circuit, and ideally want to get a histogram of a certain parameter affected by that noise over many runs. However, when I use the white() command in LTspice, or ...
94 views

### Photon count with ADC, am I doing it right?

I have this LED and I want to characterize this photodiode. The LED should produce light of 370 nm, but I measured it and it is around 358 nm, and at that wavelength the quantum efficiency ($\eta$) ...
108 views

### Headphone Noise from Laptop SMPS

I have been facing an issue that has been a mystery to me for quite some time, and I wanted to see if someone here can potentially give me more insights on this so I can understand why it is happening....
94 views

### How to suppress noise in my circuit

I illustrated what my circuit do as you see. Switching frequency is 800 Hz. When I increase the load, a noise is heard from my circuit. Here is my drain oscillocope view in frequency domain. What can ...
70 views

### Differentiator circuit sees noise on PCB after 2 min

I'm new to PCB design, and looking for some advice. I designed a PCB shield and I'm seeing a lot of noise in my differentiator circuit. The circuit will run perfectly for about 2 min and then all of ...
137 views

### Noise for a switched capacitor circuit

I have a switched capacitor circuit that looks like below: It operates at 80MHz to realize a 625k resistor. It works fine in the circuit. I tested with VDAC(input)=1.8V and the voltage at the right ...
280 views

Description of the situation I am trying to get an analog vibration sensor signal to a Raspberry Pi 3 B+. To convert the analog signal to digital values, I'm using Waveshare High-Precision AD/DA ...
218 views

### What effect does a logic analyzer probe have on a circuit?

I have an MCU controlling a LED sign. This sign speaks the HUB75 protocol, which is essentially a large shift register. Being a shift register, this requires a clock signal to be generated, which the ...
85 views

### What is the signal-noise model of laser induced fluorescence?

The following image is an example of a fluorescence signal trace from the photomultiplier tube detector (PMT). Each spike represents one fluorescently labeled cell. This signal model is definitely ...
608 views

### Noise problems in current sensing

I have the following circuit: simulate this circuit – Schematic created using CircuitLab I am using a motor from an electric bike, as a generator and I am rotating it using a drill, to test ...
17 views

### Mux switching one leg of differential signal

I found the schematic below for a muxed thermocouple circuit from this web page. This circuit uses a mux to switch just one leg of the thermocouples. While I am sure that this works fine I have a ...
61 views

### Filter VR-sensor to MAX9926

I have an issue with a noisy VR-sensor signal that my MAX9926 IC isn’t managing to interpret correctly, and instead outputs rubbish. The wheel that’s being used has one long tooth and one short. Here ...
59 views

### How to protect my 555 timer against DC motor noise?

I have this circuit: (Sorry for such a bad schematic.) As you can see, there is a DC motor that gets power from 12V source, using a NPN transistor controlled by a 0-5V signal. Please note that ...
191 views

### Thermal Noise in Oscillators

let's consider this circuital model for an LC oscillator in which the parasitic resistance R is affected by thermal noise (represented here with an equivalent noise current source, according to the ...
29 views

### Ethernet Link is going down while applying EFT pulses on Power Port

We have conducted our system for EFT test as per IEC-61000-4-4. We have applied EFT on the AC side of the AC-DC power supply. We are using the power supply HWS50A-12/A from TDK-Lambda. As per the ...
36 views

### 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 ...
167 views

### GSM noise from a 2-layer PCB with SIM800C

I've designed a 2-layer PCB that contains a 12-5V buck converter (P2576L-50 - a Clone of the LM2576), 3.3 (AP1117-33) and 4V (MIC29302WU) shunt regulators, an STM32 micro and a SIM800C GSM module. ...
72 views

### Need help troubleshooting Teensy 3.6 SPI to DAC8568

running out of things to check with this problem I'm having. I designed a board around the Teensy 3.6 microprocessor, and I wanted to connect a DAC8568 chip to it for some analog outputs. It works ...
63 views

### How to remove DC power supply noise while load is active?

I'm using a breadboard power supply to power up two STM32F103, two Hall flow sensors, one IC555, and one 16x2 LCD with backlight. While everything is connected I have alot of noise in the system which ...
82 views

### What is the relationship between dark current and the contribution of dark noise in a photodiode?

For example, if I have a datasheet for a photodiode that lists a dark current of 1000nA. I have a transimpedance amplifier with 1kohm transimpedance and 1 mV voltage output voltage noise. Presumably ...
40 views

### SMPS mains hum on guitar rig

My guitar rig consists of Guitar -> Audio Interface (Steinberg UR22) -> Laptop (via USB). I listen to the (processed) audio using headphones connected to the audio interface. ISSUE: When the ...
144 views

### Signal noise cancelled by touching the leads

I have a pressure sensor that outputs 0.5V with a +/- 20 mV noise. I am trying to identify the root cause of the noise using an oscilloscope. The noise occurs in waves of twice the mains frequency, ...
199 views

### Questions about a design for an SMPS post regulator filter circuit?

For minimizing SMPS ripple and especially noise, I’m trying to make a small interface which is a post regulator cascaded after an LC filter. I have come across some papers related to this topic and ...
192 views

### Reduce Noise Added With Zener Clipper

I'm working on a hobby Arduino project to create an audio visualizer using an LED strip. I'm using the MSGEQ7 to separate the signal into 7 bands, then send it to a Wemos D1 Mini. I started by ...
151 views

### Identifying Noise in 12AU7 Based Headphone Amplifier

I've been working on making a tube based headphone amplifier as a fun personal project. The amplifier is based around this 12AU7 vacuum tube. The project for the most part is following this existing ...
70 views

### Noise immunity of single ended analog voltage signal

I want to use a sensor with analog output in my design. The output of the sensor is a low frequency traingular wave (less than 300 Hz) and voltage vetween 0 - 5V. I need to carry the sensor signal to ...
130 views

### What is the reason for high frequency noise when amplifier is powered with battery?

Hi I made a small headphone amp and powered it using lipo battery.voltage is stepped up to 5v.everything is working with direct supply (ie., while charging battery)but as soon as I unplug the charger ,...
57 views

### IR emmiter and reciever layouts for custom sensor

I'm having a hard time designing a PCB for a sensor array that need to detect if there is a small reflective object (3-20 mm section) in the way. That object can slowly rotate around a shaft. I have ...
352 views

### Noise resilient, hot-pluggable communication bus over long cables?

I'm working on a setup, where we need communication between a master device and several slave microcontrollers distributed out in different boxes connected by "long" cat5e cables (3-10 meters) The ...
227 views

### How to reduce the effect of electric lighter noise on Micro controller?

I am using a kind of electric lighter in my circuit in order to turn the fire on. And also i have used some sensors that alert in danger by sending a signal to the MCU (ATmega 32) interrupt. The ...
525 views

### Modded speakers emit high frequency noise, how to filter it out?

I came up with an idea to convert my PC speakers into Bluetooth speakers. It's not really a serious project, rather a proof of concept, but I want to get it to work as well as possible. Here's my ...
293 views

### SMPS output noise: Why is it amplified further away from the output capacitor?

Well this is just a general question about switch mode power supplies, but i have recently built a buck converter, and read that it is very important where in the circuit you place your probes, to ...
714 views

### RS485 ground noise problem

I'm using the USB FTDI dongle to convert USB to RS485, half duplex, 3 wires (A+, B-, GND) with 115200 baud rate. I'm working with controller of NXP (K64) and I'm experiencing random tx enables on the ...
163 views

### Noise in FET reverse-polarity protection for ADC

I have quite precise ADC circuit. I want to protect input supply voltage (not ADC input) from reverse-polarity using FET transistor as shown on the picture below. I wonder: is there any noise / worse ...
185 views

### How does this diode improve the common mode conducted noise?

This image was taken from UCC28881 (page 16) The desciption in the body says: A half-wave rectifier is chosen and implemented by diode D2 (1N4937). It is a general purpose 1-A, 600-V rated diode....
523 views

### What's necessary to properly decouple/filter a PWM-controlled fan from an Arduino?

I've got a small problem I could use some help with. I am using an Arduino to control a cooling system I am building for a DSLR. Primary goals are to use PWM and some pots to control TEC power, as ...
96 views

### Relay+SMPS = Noise in RS-485 bus

I designed a board with a microcontroller (Atmega328), 3 relays and a RS485 transceiver. The relays control SMPS LED drivers (Meanwell LPF series). The system consists of 10 boards, each one ...
54 views

### Is it really necessary to ground the metal can on crystal oscillators?

I am modifying a KOSS portable dvd player into a portable raspberry pi computer and have noticed that they grounded the can of the crystal that feeds their microcontroller. I am curious if there is an ...
44 views

### Random Electrical noise LM386

I tried to make a microphone (condenser microphone) amplifier that powers a 0.5W 8 ohm speaker using the LM386, however I have been having random noise issues. Whenever the power is connected, the ...
36 views

### STM32F4 DSP noise with inbuilt ADC and DAC

I'm trying to perform signal filtering with STM32F407VGT. I've set up the ADC and DAC to work synchronously, triggered by a timer at 42kHz, and using DMA. The idea is to process half of the buffer ...
29 views

### Boost converter - low inductance and discontinuous or high inductance and continuous?

I'm working on a battery powered application and I need to step up from ~3v to ~25V. I'm trying to balance the peak battery loads vs the overall performance. I'm torn on the inductor. I'm at ~2MHz ...
57 views

### Ripple on tens-millivolts sinus waveform

I’m trying to make a DDS to generate a sinusoidal signal with tens to hundreds of millivolt amplitude and hundreds kHz frequency using an LTC1666 DAC. But I have some confusing results. Device ...
61 views

### Noise generated by monitor from Word document

I was zooming in and out of Word documents of only text and noticed that a noise was produced. The noise increased in pitch as I zoomed out and decreased as I zoomed in. I tried changing the font ...
33 views

### Problem in deriving Noise Figure for Cascaded systems

I am trying to derive Noise Figure of Cascaded System. I am making some conceptual mistake somewhere in derivation and getting wrong answer. Can any one please help me figure out where I am going ...
70 views

### Unstable current source when reaching a certain threshold in current draw

I’m currently building a system for automated testing of ECUs. It consists of an ECU with regulated loads connected to its power outputs. The other IO of the ECU is connected to an IO expansion card. ...
77 views

### How can I reduce noise caused by shift register updates?

I have a couple of designs using 74HC595BQ-Q100,115 shift registers. Some are using the SO-16 package, some the DHVQFN16. Some have five shift registers, some have three. ALL have a significant ...
96 views

### Will a 2.4GHz WiFI/Bluetooth antenna create noise in my sensitive EEG measurement circuit?

I'm designing a circuit for doing EEG measurements and I want it to be very compact. As a result, the WiFI+Bluetooth antenna (2.4GHz) will be sitting half an inch above the electrode inputs. Will this ...
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 ...