Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [low-pass]

A low-pass filter lets lower frequencies through and blocks or reduces higher frequencies.

See also , high-pass, band-pass, band-stop

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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. Based on what should I prefer one over the…
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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?
DragonDude
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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 after 10kHz. Why is that, and why would I use a…
Christian
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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 capacitor, the frequencies targetted by decoupling caps?
Rafael
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Understanding the AVCC pin wiring on ArduinoLeonardo (low-pass filter?)

The Arduino Leonardo has an interesting difference with previous boards: the AVCC pin of the ATMEGA32U4 is connected to +5V through a MH2029-300Y ferrite beads and to GND through a 1uF capacitor. In ArduinoUno and ArduinoMega2560, this pin was…
sarfata
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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 a capacitor cannot instantaneously change, but…
sherrellbc
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Question about RC charge-discharge curve

I found the following image on electronics-tutorials.ws: Isn't this wrong? Shouldn't the voltage rise faster during the first 2T than that it decreases during the next half period? I think so because the voltage difference at t=0 is Vc, which is…
flup
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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 like a variant of a Sallen-Key low pass filter,…
Linus Tielemans
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Low pass filter with two capacitors?

I'm trying to drive a speaker from an ESP8266 for a project, and found an article suggesting (ab)using I2S as a 1-bit Pulse Density Modulation DAC. Apparently that's pretty noisy, so the article gives the following circuit diagram for the low pass…
Garth Kidd
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Significance of cut-off frequency in a low-pass filter

My question is: why do we choose cut-off frequency to satisfy that the magnitude of transfer function \$ H(\omega) = \frac{1}{\sqrt{2}} \$? Therefore I am not asking how cut-off frequency is calculated as \$ \sqrt{\frac{R}{L}}\$, but I am asking why…
Binary Yildirim
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Why does my electret microphone amplifying and filtering circuit output so much noise?

Background information I'm currently designing an input conditioning circuit that amplifies and filters an electret microphone signal in preparation for the signal to be processed by an ADC (analogue to digital converter) and written to an SD card…
SIMPLY MARC
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What is wrong with this butterworth filter, how can it be improved?

I have designed a 6th order butterworth low pass filter with 20KHz cut off frequency using Sallen Key topology (thanks Andy Aka). The filter is behaving as expected with the cut off frequency and roll-off however, several order of magnitude above…
quantum231
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How to Calculate Complex Low Pass Passive RLC Filters?

I have designed a FPGA based DDS and now I want to add a low pass filter to its output. Previously I was working on a project based on AD9850 DDS(0-50MHz) and I had a commercial module for it that had a low pass RLC filter which worked excellent (…
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Decoupling Capacitors: What happens to the DC on the cap once noise is introduced and it shorts?

simulate this circuit – Schematic created using CircuitLab I've been using decoupling caps for a while now and I understand their purpose in keeping DC signals clean since capacitors allow high frequency signals through that get passed into ground…
OhmerSimpson
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Why a low-pass filter applied to a square wave gives a weird wave?

When a low-pass filter acts on a square wave, the output is something similar to this: My question is simple. If the filter is a low-pass filter, it should filter all frequencies that are above some constant frequency (the value will depend on the…
felipeek
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