A filter modifies signals based on their frequency.

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36 views

How to find Magnitude of transfer function

I am trying to read a paper by Butterworth on his filter. There is a term called filter factor which is said to be the ratio between output emf by input emf.But i am not able to understand the ...
3
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3answers
77 views

Design help! — Play a pure tone into a mic and depending on its frequency a specific LED will light up

I'm still new to electronics and am making this in order to learn more about circuit design and filters. I do not want to use microcontrollers. I want a purely analog solution. I'm trying to make a ...
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0answers
36 views

How dimension a LC filter to pwm signal [duplicate]

Hello, as you can see in shecmatic , I am creating a PWM signal by comparing a sine wave (50Hz) and a triangular wave (10kHz) which is within the block "PWM(10khz).... in ordem to control a full ...
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1answer
43 views

Automate Noise Sensitive Designs of SMD For 95% Sensitivity

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 ...
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1answer
47 views

band pass filter on solar cell to detect laser

my target is detecting a laser generated with 1k frequency using a solar cell, i'm using this idea which is using a band pass filter on the solar cell to block the dc sun light and let me detect the ...
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1answer
36 views

2nd order Sallen-Key Bandpass filter design in Matlab

I'm trying to design a Sallen-Key BPF within Matlab. With the documentation found on ti: http://www.ti.com/lit/ml/sloa088/sloa088.pdf, I studied and understood the basic. As for the design: The ...
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2answers
57 views

What is the pole frequency of a three-phase LC filter?

Suppose I have this configuration: Assume L1=L2=L3 and C1=C2=C3. What is the pole frequency of this filter? Edit: As mcmiln says, this is not identical to the question here: Cut Off Frequency in ...
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0answers
18 views

Harmonic distortion sweep in QUCS

Is there a way to measure THD or THD+N vs frequency in QUCS? THD+N: It would need a notch filter that tracks the AC sweep to remove the stimulus signal, and then compare the RMS amplitude before and ...
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20 views

Post amplification filtering

I'm trying to construct a guitar cabinet, and currently have an odd setup. Here's a visual: http://postimg.org/image/g6nl0zuq9/ The circuit is: Amplifier(+)->S1 S1->S2->S4->Amplifier(-) ...
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1answer
115 views

Is it possible that my UV LED is emitting white light? If so, how would I filter out the white light?

I recently purchased a 365 nm UV LED, and set up the proper circuit. When I turn the power on, the LED lights up very dimly. Is this white light (that's the color I saw) being emitted from the LED? ...
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0answers
55 views

How to drive a capacitor from an AC current source

I am wondering how it is possible to drive a constant ac current through a capacitor. I would like to use a transistor as the current source/sink. The problem is that if I put the capacitor in the ...
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3answers
87 views

why is noise always a high frequency signal ? what then is frequency of a noise?

while designing signal conditioning circuits for sensors , we design low pass filters to remove high frequency noise. why can't noise be a low frequency signal or what will its frequency be ?
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1answer
56 views

Add Low Pass Filter to existing Stereo Amp Circuit

I have designed a simple stereo amplifier which is attached below, but the bass output was bit poor. So I'm planning to add extra low pass filter circuit to this circuit. I don't have any idea how ...
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2answers
46 views

Filters and Accelerometers

I have just started working with the accelerometers and have referred few docs related to same. So I came across the filters used in accelerometers. I need to know, Why are there filters in the ...
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0answers
50 views

FDNR instability

Can anybody advise me, I have made many attempts to make a practical FDNR circuit, but it is always very unstable with lots of RF oscillation. I am trying to make and audio filter, that is the ...
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1answer
37 views

how to construct an active high pass filter on breadboard

i am going to have an experiment on active high pass filters and i would like someone to tell me how could i construct / carry the experiment please i don't want be embarrassed. so tell me please ...
3
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3answers
97 views

Converting an arbitrary pulse to logic level

Background: I'm trying to measure the time interval between (4) different pulses with a baseline of ~2V and rougly 1.6V p-p . Currently I'm using the ADC on an STM32 to sample the four channels. ...
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2answers
39 views

Anti-aliasing filter as notch and lowpass

In order to reach a steep attenuation for an analog antialiasing filter, there are issues if a high Q notch filter is followed by a low order lowpass filter (or vice versa)? The notch resonance could ...
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1answer
41 views

Audio Circuit to Remove Vibrato while Preserving Word Detail

In music, vibrato describes the warble effect often added in by singers as they sing. I was trying to come up with a circuit to remove it from an audio signal, almost like a "vocal stabilizer" ...
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1answer
42 views

What is “ripple bandwidth” in filter terminology?

I'm told "ripple bandwidth" is different from a "-3dB bandwidth" or corner frequency. How is this commonly defined, and how do I derive it? My application: There seems to be a discrepancy in the way ...
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2answers
135 views

Can inductors always be avoided in analogue filter design?

Inductors have always been described as big, bulky and extensive to me in text books. It seems that people don't like them. However, I have seen that inductors do appear in filter design due to ...
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1answer
33 views

Non-resonant RLC band-pass filter

To create a band-pass filter using an RLC-circuit, i drew the following circuit (assuming R is given as 120): The corresponding transfer function is $$ H(\mathrm{j}\,\omega)=\frac{120\, C\, ...
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5answers
139 views

Blocking DC without blocking any frequencies?

Is there any practical way of blocking DC without blocking any AC frequencies (or as few as possible)? Suppose I wanted to block DC and let through all frequencies between 2Hz and 10Ghz with minimum ...
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1answer
50 views

How to filter out ringing current in a local battery telephone system?

We have a network of manually-switched local-battery telephones. Here is depiction of the circuit in one telephone: ...
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1answer
73 views

3-dB Frequency of second order transfer function

How can i obtain the 3db frequency of the each transfer function ? My attempt: My guess is both transfer functions have the same 3db frequency.But equating the magnitude to 0.707 gives a fourth ...
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1answer
53 views

Is phase angle a important thing to consider when designing filters?

Whenever I was choosing values for filters I always ignored the phase angle plots, but should I be taking it into consideration when for example designing a high-pass filter for the input of an ...
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1answer
83 views

What is the transfer function of an LCL filter?

simulate this circuit – Schematic created using CircuitLab I read that for grid-tied inverters it is common to use a LCL filter like above, to turn the PWM output from the H-bridge into a ...
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2answers
73 views

how can i filter this spikes on FFT?

i am working on very low amplitude signals and sensors. I have recorded one hour data. And i am looking its FFT graph. You can see FFT image. My question is that, what can cause the spikes in FFT ...
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1answer
52 views

Second-order Band-Pass Filter Gain Confusion

If I derive the equation for a bandpass filter (in this case, critically damped) from the RLC transfer function, I get a different result than I would get otherwise by combining the transfer functions ...
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1answer
45 views

sallen key butterworth interfacing with arduino Due

I am using this stethoscope circuit I want to give TL072 butterworth filter output to Arduino Due ADC which input is max 3.3 but the supply of the mentioned circuit is split +9-0-(-9) volts. How can ...
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2answers
112 views

Type of Filter from pole-zero plot

If the zeros were on the imaginary axis, it sure would have been a NOTCH filter. But, since the complex conjugate zeros are on the left of the jW axis, the transfer function has second order terms ...
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0answers
64 views

Find R and C in a RC low pass filter

The Question goes like this: In the input of measuring systems a RC low-pass filter is placed. The desired signal is at a frequency of 1KHz and amplitude 1V, but in series with it is a ...
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2answers
38 views

Help understanding VCF schematic

I'm trying to build an adjustable active filter for an audio mixer and stumbled upon this design. I'm completely lost. I understand first order passive filters and Sallen Key's.
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1answer
49 views

Music Controlled LEDs [duplicate]

I know there are tons of examples of music driven LED circuits out there, but they mainly control just one LED or one string of them. I want to make a circuit that will control quite a few LEDs, with ...
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1answer
76 views

How to design a band-pass filter with 2.4GHz center frequency? [closed]

my graduation project is "study and design of a band-pass filter" with center frequency 2.4GHz , i want to know how to design its cct. and which concepts i have to follow to determine the values of ...
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27 views

Chebyshev filter design.

hello, I am really stuck with this question, I was wondering if anyone could help me with it? like I am not sure which way is best to approach it
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1answer
37 views

Is there a way to proof that you don't see the cut-off frequency in the plot?

In my previous question, I've asked something about acut-off frequency (Finding the cut-off frequency). But in my plot I don't see those, I see the one that I find when I pick the zero and the pole ...
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1answer
46 views

Summing Amp Response in a Cascaded Butterworth Notch Filter

I'm having trouble with a cascaded butterworth notch filter I'm designing and was hoping to get some insight on the summing amplifier stage at the end. I'm still a student, so my question may be a bit ...
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3answers
49 views

Analog filter resistors and capacitor tradeoffs

I am designing a filter to obtain a dc reference from a signal, and I am thinking about using the schematic below for a cutting frequency of 1 Hz: simulate this circuit – Schematic ...
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3answers
261 views

Source of Audio Noise at Low Volume — BlueTooth Mini Amp board

I'm still learning some of this stuff. This is the first time I'm really using an oscilloscope in a few decades. I picked up a small bluetooth only audio amplifier board. Puts out a whole lot of ...
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2answers
57 views

Theoretically determining Q for an inductor

I've recently been looking into passive filter design a little more closely than my classes have gone into, so far as actual component selection and design are concerned. The biggest sticking point ...
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4answers
108 views

When to use an active filter instead of a passive filter? [closed]

I want to build a low-pass or a band-reject filter to remove 50/60Hz humming noise. I couldn't decide where to start with. I will use this filter to remove 50Hz noise where I make data-acquisition of ...
5
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4answers
132 views

Is there a clever way to use a small variable capacitor where a larger capacitance is required?

I am designing an activity where students should band pass a song to find a hidden message at 1000Hz. Problem I have considered using a notch filter and tank circuit, but using the formula ...
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1answer
47 views

Input filter pcb layout considerations

I have two options for input filter having ferrite bead and reverse polarity protection diode as shown below simulate this circuit – Schematic created using CircuitLab The input supply ...
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0answers
61 views

How to measure the rolloff/corner/cutoff frequency in LTspice with a MEAS statement?

In hspice you can do .MEAS AC corner when VDB(out) = -3 to get the -3dB rolloff frequency. This syntax doesn't work in LTspice (I suspect because VDB is not ...
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3answers
137 views

Opamp filter - oscillator

Here is my task: How to solve this? I'm confused because of only one input in opamp. Edit: Here is solution: But I'm still confused why is there only one input to opamp
3
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1answer
67 views

Conducted Emission Fail at Low Frequency

I need assistance to understand why conducted emission test performed by one of our Customers using our Filter failed at low frequency of 205KHz. The filter is a planar capacitive filter of 47K±20% ...
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1answer
95 views

LPF (LC) filter before LDO for DAC

we have a switched power supply with a sw frequency at around 70Khz In our DAC pcb , we use LDO with a pssr of about 60db reduction at 70Khz We are thinking to add a LPF (LC or PI) before the LDO to ...
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2answers
70 views

Voltage Controlled Butterworth Hi-Pass Filter using a Transconductance Op Amp?

In the Texas Instruments datasheets for the LM13700 Transconductance Op Amp (as well as the earlier National Semiconductor versions) there's been an application note showing a voltage-controlled 2 ...
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1answer
49 views

Low pass filter on PSU and target amplifier

we are designing a LLC resonator PSU to feed a class D amp The switching frequency of the LLC PSU is 80-140Khz. At the end of the PSU we are thinking to add a LPF ( PI filter ) with a cutoff ...