Questions tagged [filter]
A filter selectively processes input signals in frequency- or time-domain.
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My linear voltage regulator is overheating very fast
I'm using a 5 V / 2 A voltage regulator (L78S05) without a heatsink. I'm testing the circuit with a microcontroller (PIC18FXXXX), a few LEDs and a 1 mA piezzo buzzer. The input voltage is aprox. 24 ...
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My understanding of RC circuits is broken
I asked a relatively simple question. Unfortunately, the answers provoke far more questions! :-(
It seems that I don't actually understand RC circuits at all. In particular, why there's an R in there....
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What is impedance?
This is presented as both a resource for the community and a learning experience for myself. I have just enough knowledge of the subject to get myself into trouble, but I don't have the best grasp of ...
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What is the purpose of a capacitor to ground?
I have here a filtering circuit from a microwave. What is the point of the capacitors to ground. Another answer in a previous question of mine said they were used for filtering however I don't ...
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Why would you stack a resistor and capacitor on top of each other?
I've inherited an charge amplifier/shaping circuit from my predecessor. When he wanted to make a low-pass filter with current-to-voltage conversion, he had a standard circuit like:
simulate this ...
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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 ...
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Why should I use digital filters rather than simply manipulate signals in the frequency domain and then recover them into the time domain?
I'm quite a novice in signal processing and I know this question may be too broad. But I would still like to hear hints from experts.
I was taught to use butter (...
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How do I choose component values when designing a Low/High pass RC filter?
The cut-off frequency of a RC filter is obtained from the well known equation,
$$1\over(2 \pi RC)$$
This is one equation with two variables. For example, R=100, C=10 has the same result as R=10, C=100....
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I think I found an error in an electronics book. Are my equations correct here?
I'm reading Practical Electronics for Inventors, 4th edition, to freshen up my long forgotten knowledge of electronics. I love the book so far, but I just came across an equation there which seems ...
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Why are there so many vias on this board?
I was looking at the MMZ09312BT1 development board layout, and I was curious about all the holes they have on the board. Are these vias? What is their purpose (I heard somewhere that they are meant as ...
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Why use a resistor in filter circuits
Since capacitors and inductors can filter on their own. Why are separate resistors needed? For example in a RC circuit, using only a capacitor would be different in what manner?
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Is a capacitor a high-pass filter or a band-pass filter?
This has been bugging me for a while now... Does a single capacitor, on its own, behave as a high-pass filter or a band-pass filter?
In a crystal radio set, you use a single capacitor as the tuning ...
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How to identify filter behaviour without memorizing different topologies
Is there a way to tell if a circuit is high or low pass without memorizing different topologies?
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Why are caps configured this way in EMC filters?
Every EMC filter I've seen has capacitors between the AC lines and earth, configured like this:
simulate this circuit – Schematic created using CircuitLab
Why are the caps not configured like ...
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What does this schematic symbol marked SG1 looking like two arrows pointing to each other represent?
I know the symbol at the bottom is ground, but I can't get what the other symbol is. It can be a single symbol of two arrows pointing at each other, or two symbols each one a arrow.
I also have the ...
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Analyzing Accelerometer data characteristics and designing a filter
I have about 32 seconds worth of accelerometer data of a basic driving scenario 25MPH normal roads along with hitting about 7 potholes and a rough patch of road. The accelerometer is mounted on the ...
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Why does increasing the sampling rate make implementing an anti-aliasing filter easier?
From an answer to a question regarding sampling rate and anti-aliasing filter I read the following:
The closer you get to the theoretical minimum sample rate, the more
difficult the analog filter ...
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TVS diode before or behind resistor
The best way to protect AVR pin for me is RC filter and TVS diode but I don't know one thing. I've seen schematics where TVS diode was before RC filter like in first schematics.
simulate this ...
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Understanding bootstrapping in analog active filters
"Bootstrapping" is a common technique in (analog) active filters, where the output of the filter is fed back to a node that would otherwise be connected to ground.
For example, the Sallen ...
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What's the sharpest frequency response for a non-causal low-pass filter whose step response doesn't overshoot?
Butterworth, Bessel, Chebychev, and sinc low-pass filters are used in various cases where there are different tradeoffs between having a uniformly-decreasing frequency response, a uniform phase ...
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Design a filter that allows frequencies below 5 kHz to pass freely, but all frequencies above 5.2 kHz must be undetectable
My biggest challenge with this question is its ridiculously steep roll-off rate.
I am assuming that the signal is undetectable if its gain is -20 dB. This means that, within the transition band of ...
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Why too many capacitors in parallel for Vdd supply net? Can't we just add all to replace with one big capacitor?
Here is a schematic of a Basys-2 board's power regulator IC and filters. It is just an example but this is fairly similar to many designs I've seen.
Why are there so many capacitors added in parallel ...
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Why have a 0.1 uF capacitor in parallel with 2500 uF in a power supply filter?
I'm troubleshooting an old solid-state bass amplifier (Ampeg B-15). The power supply has a 56 VAC transformer tap into a 4-diode full bridge rectifier circuit.
One side of the bridge goes to ground. ...
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What is the advantage of a Sallen-Key filter over a normal second order filter?
Wikipedia links to a Sallen-Key filter as a active low pass, so I tried it out with LTSpice.
The frequency response and phase response are not linear, instead frequency response even gets higher ...
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Why don't decoupling/bypass capacitors need resistors to perform their function, like regular filters?
Why don't decoupling/bypass capacitors need resistors to perform their function, like regular filters?
Is it because the stray resistance of copper traces is enough to filter, along with the ...
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Ripple voltage filtering capacitor
I'm an self-taught high schooler who's trying to understand how filtering capacitors work. I've searched and read multiple websites trying to understand how filtering works. At the point where I am, I'...
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Good filter design software for Mac OS X/Unix?
I need to implement a simple lowpass filter for a data acquisition circuit (using stretch conductive fabric as a resistive sensor). Various sources have recommended that the best way to go about this ...
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Audio Amplifier Op amp
I'm trying to design a circuit in which a microcontroller produces a signal and then using an amplifier drives an 8ohm speaker.
I've so far used LM386, but it cannot go above 1W, which turned out to ...
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Distribution of component values with a given tolerance?
Suppose I have a collection of parts with the same nominal value and some tolerance, say 50 Ohm 1% tolerance resistors. What distribution of actual component values can I expect? I can imagine ...
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Twin-T Active Notch Filter Analysis
Could anyone give me a hint in analyzing the Twin-T Active Notch Filter?
I tried a delta-star transform, followed by nodal analysis, but ended up with conflicting equations. For an example, look at ...
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Troubleshooting a faulty filter circuit in a PAL CRT display
I have an old CRT monitor (Phillips CM8833) which I am attempting to repair. When displaying a composite PAL signal, it only shows a black and white image, but it is still able to display RGB signals ...
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IIR filters what does infinite mean?
I am having difficulty understanding what "infinite" in IIR means in practice..In theory the impulse response is used for feedback..If this feedback never ends how output is generated?
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How to analyze this circuit in the time and frequency domain?
I came across this circuit in another post and started looking at the op amp filter and how to apply traditional circuit analysis ( using 1/jwc for capacitors) and couldn't derive the transfer ...
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Do I need a 50/60Hz notch filter for battery powered devices?
Given that battery powered devices are not plugged in the mains power, can I assume that there will be no 50/60 Hz frequency noise?
This question came up while thinking about what the circuit for a ...
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How to compute input impedance?
I use a Sallen-Key filter for a project at university and I need to know its input impedance. Is there a way to compute it theoretically ?
Here is my circuit:
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Adding an anti-aliasing filter to op-amp before ADC
I am designing a circuit that is intended to capture audio samples from multiple channels for sound source localisation.
Each channel has the following 2 stage op-amp circuit, before going into a ...
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Are there any quick way to tell if a filter is high-pass, low-pass, or band-pass, just by looking at the transfer function in the s domain?
How can I quicly determine if a given filter's transfer function like: \$ H(s)=\frac{k}{s^2+ks} \$, or \$H(s)=\frac{1}{s+k}\$, is either a low-pass, high-pass, or band-pass ?
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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. ...
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Why is the output of a filter considered 70.7% of input while determining the cutoff frequency?
I have seen in many books that while finding the cutoff frequency of a filter (from the transfer function) the output is considered 70.7% of the input.
Why 70.7%?
Why not 50% or 20%?
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Bridge rectifier: What is the purpose of these two elements?
I found the following circuit in a random video (don't know what it's worth) and have two questions about it. I get that it's a full wave rectifier, and I think I have a decent idea on how it works. ...
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How does an emitter follower work as an AM detector?
Can someone explain how an emitter follower used as an AM detector (shown below) actually works?
I don't get how a (theoretically) linear system like an emitter follower would work as a detector when ...
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Cut-off frequency, gain and quality factor calculation of complex 2nd order low pass filter
I'm building a full analog chorus-effect pedal. My schematic is based on that of a Rockman X100 headphone amp, designed by Tom Sholz. In this schematic, there is a 2nd order low pass filter that looks ...
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Difference: Low Pass Filter and Large Capacitor?
When working with microcontrollers it is recommended to place filter/decoupling capacitors between a supply pin and ground. I understand the purpose of this implementation, namely that voltage across ...
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Intuitive explanation for filters
Can anyone provide an intuitive explanation for the filtering action of RC or LC circuits? I know the mathematical treatment involving reactances but I was wondering if that could be explained ...
9
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Gain in Sallen-Key filter
How can we increase the passband gain in a Sallen-Key type low pass / high pass filter, preferably without using additional op-amps.
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Function of Specific Capacitor in Audio Amplifier's Negative Feedback
The audio amplifier that I am referring to here consists of three stages. Among others, the amplifier also includes negative feedback (NFB) that is made of two passive resistors.
From the base of TR3 ...
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Use of 100K ohm resistor along with 0.1uF capacitor?
In the circuit diagram below, why is there a 100KΩ resistor (NOT R2) connected to the capacitor? To my understanding the capacitor-resistor act as a high pass filter to block the DC offset of ...
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Methods of filtering noise caused by DC brush motors
I am looking for any information that would help me reduce the power rail noise and EMI of DC brush motors. I am building a robot that is powered by 2 x 250 W 24V DC motors.
Thank you in advance
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Is it possible to make a weak analog low-pass filter with less than 20 dB/decade roll-off?
Part of Respawned Fluff's answer to this recent question on headphones got me thinking about low-pass filters:
It seems they actually invert the transfer function of the dummy head/ears via ...
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Cleaning power rail from switch mode power supply
In my circuit, I do not have control over what the power supply is used. Thus, I am preparing for the worst where a cheap noisy SMPS is used. I have some ADCs down the line that get their power from ...
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