Questions tagged [noise]

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

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9
votes
3answers
17k views

How to filter noise from ground?

I have an audio application scenario here. The Idea is to power a device (that later produces sound) with USB. Unfortunately, I have massive static and what sounds like pink (Brownian) noise on GND. ...
7
votes
4answers
4k views

Advice on cleaning up 5VDC from a wall-wart

Assumption: I think it's generally true that commercially available AC/DC wall-worts can be expected to be pretty noisy (e.g. you can't count on much better than 5% stability). Background: I'm ...
20
votes
6answers
4k views

How to combat noise from my circuit polluting my 12V rail?

I made a controller for 12V DC fan. It is basically a buck DC-DC converter controlled by voltage. It regulates voltage for fan from 3V (lowest speed, fan draws 60mA @ 3V) to 12V (full speed, fan draws ...
14
votes
7answers
11k views

Is there any downside to using a larger than needed smoothing capacitor?

I work with low-power DC voltage regulators. I am already aware of the formula to calculate the size of smoothing capacitor(s). This can be an iterative process of testing one size with a scope and ...
12
votes
1answer
3k views

Noise problem with buck/boost switching regulator

I am designing a electrical device for a research project (I'm a PhD student, but unfortunately not EE!). More info on the device can be found at http://iridia.ulb.ac.be/supp/IridiaSupp2012-002/ The ...
10
votes
1answer
2k views

How serial resistors actually reduce EMI?

I am recently working with a GSM based system, and there was this advice in the datasheet of the GSM module: 22 Ω resistors should be connected in series between the module and the SIM card ...
8
votes
2answers
325 views

Opamp noise: When is a resistor in the signal path?

I am confused as to when a resistor is considered to be in the signal path and when its not when it comes to opamp noise calculations. For instance, take the following circuit: simulate this circuit &...
7
votes
5answers
4k views

Low-noise audio-frequency BJT? [closed]

I found myself looking for a low-noise PNP transistor the other day. I couldn't find any parametric searches that listed noise performance. Even from the transistor manufacturers. You can search by ...
5
votes
2answers
3k views

Inductor selection for obtaining a noiseless analog power rail

I interface an image sensor, and the design schematic for power supply is: How do I choose one from the available 3uH inductors based on the specs? I figured the maximum current and dc resistance ...
2
votes
4answers
13k views

How to decrease distortion/noise of LM386 amplifier at max gain and volume?

From my previous question, I've made LM386 amplifier and it works better than LM1458 amplifier. I've added gain and bass boost in my LM386 amplifier. How to decrease distortion/noise of LM386 ...
36
votes
4answers
2k views

Identifying Source of Periodic Artifact at Op-Amp Output

My MAX44251 dual op-amp has a very small unwanted 131KHz periodic artifact at the output, seemingly regardless of how it's configured. My assumption was EMI, but I can't see this 131KHz signal on any ...
13
votes
5answers
775 views

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 ...
4
votes
4answers
4k views

Ground plane directly underneath physically large 100 µH inductor?

I plan to use a physically large ferrite core inductor (Murata part "1410478C", 100 µH at 1 kHz) in a 12 V, 7 A DC filter circuit. It will be mounted on topside of a four-layer PCB ...
4
votes
2answers
808 views

How does Hybrid Ground Works?

The text that is above the figure is from my textbook and i am having difficulty to understand what it is trying to say because it's not in detail!! why only remove high frequency and prevent low ...
4
votes
1answer
3k views

What is the effect on noise immunity of a floating shield on a shielded twisted pair

We have an installed system where resistive sensors are connected to some electronics by shielded cables of between 2 and 10 metres. The cable is a twisted pair sheathed in a stainless steel braid. ...
3
votes
3answers
5k views

How to clean/remove distortion/noise in my LM1458 Op-Amp?

I've made a LM1458 Op-Amp based on this video. it amplifies the input music but it produces noise and has low volume. How can I remove the noise and how to increase the volume? when i parallel ...
3
votes
1answer
2k views

Sanity check: Input and output filter for a stacked pair of DC/DC converters

In my current project, I need voltages of +/- 30V and +/- 15V for analog control purposes. The current on the 30V rails is fairly limited, ca. 70mA max on one rail and <10mA on the other. The 15V ...
3
votes
3answers
11k views

RS485 noise problems: signal ground / common ground / isolation?

I'm experiencing a lot of noise in an RS485 network I've put together using ST485 chips. The cable lengths are very short (<1m total cable length), I'm properly biasing the A and B signals and I've ...
9
votes
4answers
5k views

Remove audible noise generated by buck converter

I'm dealing with a buck converter using an ISP452, an inductor and a capacitor to act as a buck converter driven by a PWM signal coming from a microcontroller. Some part of the circuit is producing a ...
7
votes
1answer
2k views

Generating thermal noise from a resistor

I'd like to create a random number generator based on thermal noise from a resistor, using an opamp to amplify the noise and an inverter to convert the resulting spikes into a digital signal. Here's ...
6
votes
2answers
2k views

Proper method to filter inputs of a (true) differential ADC

In datasheets of different true differential ADCs I noticed two kinds of a low pass filter at the inputs. First one with 2 capacitors to the ground The other with a capacitor between differential ...
6
votes
2answers
2k views

Why is noise is considered to be a “Common Mode Signal”?

I learnt that the magnetic interference due to the Earth causes noise in the cable but I wonder why this is considered to be a 'Common Mode Signal' and why differential amplifiers are used to ...
5
votes
1answer
4k views

Eliminating the humming noise from a cheap SMPS

I am trying to build a power supply unit that powers eight 9V guitar pedals (usually pedals consume 10-100mA). So, I thought I'd buy 8 cheap 9V-1A SMPS adapters and probably fix some bypass capacitors ...
4
votes
1answer
586 views

Can a synchronous regulator “chirp” in burst mode?

I'm looking at (the millions of) buck regulators available for a project where the board will be a host board for a Gumstix Dual Cortex A9. This can pull quite a bit of current at maximum so I was ...
3
votes
3answers
355 views

Oscillation in Voltage Rectifier / Scaling Circuit

I am working on creating a circuit that will scale +/- 12v input to a unipolar 3.3v centered around 1.65v, in order to scale the kind of CV used in modular synthesis systems to work with the ADCs on ...
3
votes
1answer
2k views

Micro controller reset due to noise, PCB design for noise immunity

After making this PCB, I learnt the importance of ground plane. Besides ground plane, there is considerable amount of theory behind PCB designing which can provide immunity against ESD, surge, EMI, ...
3
votes
1answer
121 views

Techniques for Filtering a Noisy Buck Converter

I have built a buck converter on the TS30011. Unfortunately, I am getting terrible noise on the output. External Parts Used: Inductor Output Capacitors I have been analyzing my design and have ...
3
votes
3answers
744 views

Novice question about low-pass filter

I am trying to construct a simple low-pass filter for the following scenario: A high-voltage DC signal with lots of noise. I looked at Wikipedia's article on a simple passive low-pass filter. I ...
3
votes
4answers
5k views

Smaller alternative to RJ45 Ethernet connector

I am trying to minimize space usage for an enclosure that holds 48 boards with a RJ45 connector for Ethernet communication on each board. The boards work well with 10BASE-T (2 pairs) connection to a ...
2
votes
2answers
4k views

Minimization of electrical noise?

I read a textbook and it states that: "The effects of electrical noise can be minimized using circuitry external to the MCU" I don't understand how this scenario works. What does it mean with '...
1
vote
2answers
822 views

Audio Noise: ATMEGA328P, MCP4921, and LM386

I am trying to build a simple audio circuit. The goal is to store .wav files in the form of hex files in the ATMEGA328P's flash memory, and output the audio through a small speaker by using an ...
1
vote
2answers
206 views

Filtering power supply noise

I am getting 7 volts from a power supply source which I need to step down to 3.3 V for powering up my 2.4 GHz zigbee MCU (TI CC2530 + CC2592 amplifier). I am using a linear regulator to step it down. ...
1
vote
1answer
392 views

Noise from stun-gun based butane torch ignition spark is locking up ATmega328 microcontroller

I have a stun gun (http://www.amazon.com/VIPERTEK-VTS-989-Heavy-Rechargeable-Flashlight/dp/B00FPE6UN2) which I am using to create a large 1/2" electrical arc through the air to remotely ignite a ...
1
vote
1answer
8k views

Noisy Voltage Rails (Vcc, Gnd) - Noise Isolation for Automotive Circuit

I have an audio (mic, speaker) circuit that I am currently powering off of a 12V car adapter that is fed into a 10V switching DC regulator to power the rest of the circuit. I have noticed a horrendous ...
0
votes
0answers
53 views

Accuracy issues with capacitive touch screen [duplicate]

Previous question I asked here. Posting a new question because my previous approach included many incorrect assumptions. I'm working on a product with a motor, a fan, and a LCD with capacitive ...
0
votes
1answer
452 views

What could be the reason for 50Hz noise with isolated input signals?

A PCI data-acquisition board has 16 referenced single-ended channels. Here is the board: http://www.mccdaq.com/pdfs/manuals/PCI-DAS6034-35-36.pdf I'm using all 16 channels with BNC cables. The two ...
0
votes
4answers
579 views

Exact meaning of dB?

I know that when people say that a gain of amplifier is X dB, they mean that 10*log(Pout/Pin). However, How can I interpret it when they say that "noise floor is -120dB"? How can I derive voltage ...
0
votes
1answer
156 views

Effects of increasing current on external noise and SNR for analog transmission

This is a conceptual question about long analog signal transmission exposed to capacitive coupling and EMI noise as shown in below figures: simulate this circuit – Schematic created using ...
0
votes
1answer
4k views

PWM signal to SIM800 MIC noise reduction

I have an audio signal made by a PIC microcontroller using 20KHz PWM (it passes through a low-pass filter). It is very clear on an 8ohm speaker, but when I connect the output to the MIC inputs of ...
0
votes
1answer
74 views

Automate Noise Sensitive Designs of SMD For 95% Sensitivity [closed]

I am thinking of automating my noise sensitive designs of high sensitivity in SMD: maintain 95% signal sensitivity by adjusting the factors (1-3) in the thread What is the best way to layout a PCB ...
0
votes
1answer
276 views

Low current more susceptible to noise?

Supose I have an opamp with pnp input stage (constant current flowing out the input pin), like the following: simulate this circuit – Schematic created using CircuitLab Would the input from ...
0
votes
2answers
251 views

Is this definitely common-mode interference and how can I model and filter it?

A test device which can output voltage between 0 to 10V by a knob is powered by a DC adapter which converts 220V rms(meaning 311V amplitude) 50Hz AC to DC. Device is not a commercial and its adapter ...
-1
votes
1answer
618 views

Decoupling pair of microphones using noisy power source

I currently have a high quality microphone that I am powering from a relatively noisy 8V source, like that shown below. It has a built-in amplifier, and doesn't require any amplification. It just ...
-1
votes
2answers
257 views

Concept of noise floor

Can anyone please explain the concept of noise floor. If we want to design an active high pass filter with a cut off frequency of 12 kHz and pass band gain of 2, how do we apply the concept of noise ...
8
votes
2answers
2k views

What kind of effects does a relay have on signals?

Currently I'm working on a DDS based function generator. The idea is to use an AD9834 chip that will generate a triangle/sine or square wave. With some amplification electronics I want a configurable ...
7
votes
4answers
2k views

How to fix EMC problems for existing designs?

I'm going to be looking at a few products that have failed EMC radiated emissions testing and will need to apply fixes in order to make them pass (unfortunately, in these cases, two of the designs can'...
6
votes
2answers
2k views

Solving input noise

I built a very simple circuit so I could use my Bose headphones in the noisy server room without wasting batteries. I however feel silly that I did not know how noisy USB power was, thus the V(L) ...
6
votes
2answers
2k views

How to eliminate Bluetooth noise in electric guitar

After learning more about this problem, I have continued this question here. I am trying to remove noise from an electric-guitar circuit that I have created called the ArduGuitar. My circuit ...
6
votes
4answers
4k views

How does a preamplifier improve the Signal-to-Noise Ratio (SNR)?

I'm trying to understand how a preamplifier works. Is the noise not amplified the same amount as the signal? If so, how is that done in the preamplifier?
5
votes
2answers
2k views

MPU6050 accel/gyro noise that behaves strangely - what might be doing this?

I'm experimenting with an MPU6050 six-axis accelerometer/gyro reading data with a Raspberry Pi via I2C. The six-axis response makes sense in general as I rotate it by hand, rotating moves the gravity ...