Questions tagged [filter]

A filter selectively processes input signals in frequency- or time-domain.

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1answer
38 views

I/O panel filtering for shielded room

We are looking into setting up a very basic shielded chamber inside a small room at my company to be able to perform some basic relative radiated EMC measurements. We will buy a somewhat cheap ...
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1answer
43 views

Smooth signal using a capacitor [closed]

This is a full wave bridge rectifier I have read that if you put a capacitor parallel to the load resistor instead of DC pulsed signal we get a more smooth DC signal. However I am unable to ...
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1answer
50 views

Where do we place a Pi filter?

I have used pi filters in the past with the USB powers and it worked great. This time I need the pi filters to smooth out the 24V supply from a regular SMPS power adapter. There is a load switch/fuse ...
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1answer
37 views

RC low pass filter difference with RC high pass filter

This is a low pass filter: simulate this circuit – Schematic created using CircuitLab This a high pass filter: simulate this circuit If we add a load resistor to the high pass filter it ...
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2answers
65 views

Dipole antenna circuit diagram

I have this circuit : simulate this circuit – Schematic created using CircuitLab I am trying to build a radio and I need to build a band pass filter . How do I do that?
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1answer
23 views

Camera - Auto Night Vision “Mode” (ON only when dark)?

I am wondering how night vision "mode" could be automatically switch on & off in commercial CCTV? Something like this: https://www.youtube.com/watch?v=ilaXGtsx-DU (video demonstrate CCTV ...
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0answers
44 views

Removing output of low pass filter when turning off power

I'm constructing a presence detect circuit using a pulse modulated signal of 5 kHz and an infrared transmitter and receiver. The 5 kHz signal drives an infrared transmitter through a 3904 NPN ...
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1answer
48 views

DC filter for a spectrum analyser - cut off frequency

Most of the available spectrum snalysers do not want a DC component to their 50 ohm input. But how low should the cutoff frequency be? Also which parameters indicates that clearly in the datasheets? ...
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1answer
48 views

L-C-L vs Pi network

I am playing with a simple high-pass phase shifter implemented as a Pi network in Sonnet Lite with a center of 146MHz and discovered something by accident that I would like to understand: By mistake, ...
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2answers
57 views

Is this differential RC filter needed on a reference voltage?

What is the use of the differential RC filter at the end of this op amp (at least I'm seeing R100+R98+C28 as that)? P3_3V_REF is a reference voltage for the 4 ADCs in the TMS320F28377D-EP MCU. An ...
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1answer
70 views

How Do You find The Cutoff Frequency of a Low Pass Filter?

A lowpass filter exists around R1,R2,R3 and C2 but how would you find the cutoff frequency? I think that you have to first find the Thevenin equivalent circuit and this is what i got: RTH = (R1//R3)//...
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1answer
53 views

Butterworth and Chebyshev filter problem

Find the minimum order Butterworth lowpass filter whose attenuation isn't bigger than 2 dB at 5 rad/s and has 10 dB at 8 rad/s, 20 dB at 10 rad/s, and 40dB at 30 rad/s, then do it for Chebyshev filter....
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1answer
57 views

LTSpice provides incorrect bode plot

I want to replicate this structure in LTspice where the components 1, 3 et 4 are resistors with the same resistance R and 2 et 5 are two capacitors and opamp LT1356 this is the schema I made this ...
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0answers
25 views

Filtering Options for an RTL-SDR (DSP and Analog routes)

I have several related questions regarding filtering for an RTL-SDR radio. It's readily swamped by the very, very strong AM and FM radio stations local to me. So much so that your basic passive RC ...
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2answers
70 views

Importance of 2nd or 3rd order RC Low Pass Filter in noise/ripple filtering

I dont quite understand what importance does having a 2nd or 3rd order RC Lowpass filter do to filtering power rail noises. If the first stage filter only allows frequencies below 15.9 Hz arent the ...
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3answers
75 views

How can I overcome the distortion using in this circuit by using same products as we see in picture ? Or we can use 2n700 series, 3906 and 3904 bjts

Or we can use 2n700 series, 3906 and 3904 bjts. My aim is 10W, gain 100-1000 (adjustable), 50hz-20khz amplifier by using this basic components.
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Gradient based optimization for microwave filter design

In S. Amari's paper - Synthesis of cross-coupled resonator filters using an analytical gradient-based optimization technique(2000), for reducing a filter's unnecessary cross-couplings, the matrix \$[...
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0answers
21 views

Ripples in the passband of a SAW filter

In SAW Filters we have a phenomenon called TTE, Triple Transit Echos. How does this phenomenon render inband ripples different than in a Chebyshev filter? Am I also correct to assume that the ...
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1answer
43 views

Why does this high pass filter behaves like band-pass filter on Multisim AC Sweep simulations?

I have this high-pass filter schematic and its AC Sweep simulation. Until the break through the end, the graph is right but I can't see why the graph breaks on the right hand side and filter behaves ...
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0answers
28 views

Median Filter FPGA [duplicate]

I trying to build on my FPGA project median filter for 1-d vector, I need my median filter to be large, the Internet is full with references for 9 points median filter but didn't saw anything for ...
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4answers
121 views

Decoupling capacitors inrush current

My question relates to decoupling capacitors on power input rails. I see a lot of designs with MCU boards that use only decoupling capacitors and no chokes, beads, inductors, or resistors. Isn't this ...
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1answer
56 views

How can I calculate low and high frequency in my circuit?

How can I calculate low and high frequency in my circuit? I have used an 8-ohm speaker.
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2answers
53 views

Why is component spread a figure of merit for analog filters design?

Sometimes I read that in analog filter design, component spread is a figure of merit. The lower the better. What is the advantage (or disadvantage) of having a low (high) component spread? The only ...
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1answer
72 views

Second order differential equation implementation using OP-Amp

I am trying to implementat the following equation \begin{equation} x''+4x'+25=\sin(20t+36) \end{equation} using OP-Amp's. I tried to use state-space technique to implement it in the below circuit x ...
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0answers
98 views

27 points median filter

Edit: I successfully made it work, but the algorithm not efficient I taking the date coming in to my block, pipeline the data for how much points I need to median filter (for example 31), take all ...
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0answers
57 views

Low-pass (band-pass) filter for op amp circuit

I have a circuit that amplifies a one-shot inductive trigger pulse of about 1.3Khz (@780 micro sec period) from about 10-200mV to about 3-4V. Between C1 and R3 there is a 0.13uH inductor coil with 11 ...
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1answer
54 views

Chebyshev filter - theoretical vs simulation gain

Question is about the gain peak (or maybe more suitable would be growth) ocurring in higher frequencies (>20kHz) in Chebyshev filter 4-th order in simulation (simulated using Bode Analyzer in NI ...
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0answers
41 views

Crosstalk/Ghosting on ADC input

I have an ADC circuit which uses AD7689. The inputs of the ADC are driven by LT6010 opamp, and have a low pass filter . All 8 channels of the ADC (AD7689) have the same driving circuit. Every other ...
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1answer
42 views

Determine output filter using the bode approximation

Given that the carrier frequency Fc and modulation input frequency Fm are known, how would I use the bode approximation to determine an output filter, if the carrier frequency component must receive ...
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0answers
57 views

Problem understanding transfer functions of second order filters

The transfer function of any second order filter can be found by analyzing the circuit using the Laplace transform. For example the transfer function of a second order low pass passive RLC filter ...
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3answers
147 views

How can I model an optical filter using python?

Say I have an RGB LED which transmit intensity modulated signals, at one symbol transmission I want to send a symbol with all three chips.. Can I just model three bandpass optical filters like RF ...
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0answers
37 views

How to flter 70kHz signal with noise

I am trying to filter a noisy 70kHz sinusoide that goes from -2V to +2V. A factor 2 amplification should work. Any suggestion on which circuit to use? I tried to use an active bandpass filter ...
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2answers
28 views

Output Voltage Ripple Considerations

I'm working on a full bridge dc-dc converter, following the instructions on power supply cookbook. It has a 350V output and 2kW total power, 30kHz switching frequency I choose inductor current ripple ...
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0answers
41 views

Inverter EMI filter design

I'm designing an inverter with a switching frequency range of 10-40kHz. The inverter will run off of a DC power supply at a relatively low voltage (30-80VDC) and low power (~100W) for motor control ...
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1answer
28 views

Why signal coming out of a Constant K filter takes 0.5ms to stabilize?

I made a simulation of an audio amplifier with an input signal of 200 microVolts. The question is why my filter does not deliver the desired output, which operates between 512 Hz and 2048 Hz. From ...
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1answer
25 views

What does 'succeeds' and 'precedes' symbols mean in design of a peak detector circuit?

I am looking into the design of a peak detector circuit for demodulating an amplitude modulated wave. The circuit is a diode 'detector' connected to a low-pass RC filter. I have been given the ...
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1answer
20 views

How to choose input filter component value for power supply

I understand that normally we'll modify the input filter after some measurement to meet the emission standard, but does anyone know on how we can estimate the initial value of this filter components ...
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1answer
48 views

Choosing resistors in series to make standard values

I am working on designing a precision analog filter for a university electronics project. The resistance values I am using (to meet the filter specifications) are not E96 values, so I am combining ...
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1answer
50 views

Is this output normal for a capacitor filter?

I have a question regarding oscillator outputs and capacitor filters. I'm trying to build a voltage regulator. I've already calculated and tested the transformer and rectifier, and also the filter ...
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1answer
241 views

What is the advantage of RLC low pass filter over two RC conneced in series?

I guess two RC in series should be a second order low pass filter. Because the transfer function will have s^2. And an RLC low pass filter is a second order filter for sure. So what is the ...
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3answers
85 views

Modelling a low-pass filter on LTSpice to filter an input square wave at 50kHz to obtain a sinusoidal output at 50Hz

I'm trying to create a filter that filters the output of an inverter at 50kHz PWM (from reading the comments, I'm not sure if I should be calling this the switching freq?) to a sinusoidal one at 50Hz ...
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7answers
2k views

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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0answers
89 views

How to amplify the output of a digital low pass filter?

I have used the transfer function of a RC low pass filter to design a IIR Digital low pass filter. \begin{equation} H(s)= \frac{1}{sRC+1} ;First \space order \end{equation} \begin{equation} H(s)= \...
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1answer
40 views

How to choose the transfer function?

Greetings from a physics student. I have to do an activity which aim is to design a filter in frequency. To do so, I need a transfer function (gain, poles and zeros) that must meet the following ...
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1answer
71 views

filter realization help

I need a help with filter realization. I dont understand how this works. This is a multiply and accumulate filter, I dont understand why cof[0] constant is multiplied, here is the code cof is the ...
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0answers
34 views

Thyristor and c filter

I want to ask you about the usage of a c filter with a Thyristor, While doing my simulation the thyristor did not work and when i used LC filter the thyristor worked as well, do you know why?
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0answers
31 views

1/sqrt(f) low pass filter slope [duplicate]

I would like to emulate a 1/f noise source in PSPICE. If I use the EVALUE component in the Analog Behavioral Models library, and use the function RND()-0.5, I have a zero-centered white noise source. ...
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0answers
35 views

Which passive filter corresponds to this transfer function?

We've have been asked to find a passive circuit for the following function: With these coefficient values: Then, we've converted it to Laplace domain, so we have: Next, we should look for a filter ...
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2answers
46 views

How do I calculate the DC output of this specific low pass filter?

Hi! I am having some trouble understanding how to calculate the DC output of this low pass filter. Also are my calculations correcet that the transfer function of the filter is: $$\frac{R_{\text{8}}*...
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0answers
42 views

LC filter design

I want to ask you about the following graph, how can I design the values of the L and C of the LC filter? I mean is there any equations I can use for this design? NOTES: 1.This is a low pass filter ...

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