A filter modifies signals based on their frequency.

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54 views

RGB LED audio spectrum analyzer - Bandpass or FFT?

I'm about to build a coffee table which has a RGB LED matrix build in it just like in this video. https://www.youtube.com/watch?v=4NJDgvV8RZw I want the matrix to display an audio spectrum that ...
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76 views

First PSU - need help with capacitor size

I am building my first power supply unit (my first project too) and need help in figuring the size of filter capacitor (and type, though I presume Electrolytic) I need to use after the rectifier ...
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2answers
39 views

Class D amplifier woofer filter designs

I am working on a 140W class D amplifier for my subwoofer. I am familiar with its topology but have few questions. The music source is a radio that ouputs 200mV peak-to-peak signal containing all ...
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1answer
58 views

LC Low Pass Output Filters for Inverters

I need an output filter for UPS inverter. I am using 9.6kHz PWM and 60Hz frequency. Can anyone help me with the right filter as I am new with filter design?
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39 views

Why is it impossible to realize elliptic even-order filters with \$R_S = R_L \$?

Referring to RLC continuous-time prototypes of filters, I have read that an elliptic filter of even order can not have equal source and load termination resistances. The trasfer function for such ...
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1answer
57 views

Final voltage of two parallel (switched) capacitors

I am trying to obtain a resistance-circuit equivalent to a switched-capacitor circuit. It is the first stage of a ladder filter. simulate this circuit – Schematic created using CircuitLab ...
4
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1answer
125 views

Impedance matching with only capacitors?

I need to do impedance matching for 33 + j32 ohm source and 16.5 + j0 ohm load. The copper traces adds 99 ohm impedance and 20 degree electrical length. According to smith Chart below, I need to use ...
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1answer
134 views

Is this circuit block diagram correct?

I plan to build a flashlight powered by 360F 2.7V super capacitor (proposed to be charged to max 2.5V and discharged to min voltage of around 0.6V to increase capacitor life). The EMF generated by the ...
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31 views

3rd harmonic filter circuit to analyse leakage current

Anyone help me to design 3rd harmonic filter circuit using op-amp. Input voltage is 45V, 60Hz. The output should be in current 180Hz.
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2answers
40 views

Oscillating active filter

I built an 2nd order active highpass filter with cut-off frequency at 800Hz using an OPA847 (and R18=39.2k, R19=16.9k, R16=11.3k, R17=11.3k, C7=20nF, C8=20nF). Simulation works fine. In real life ...
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1answer
27 views

Sampling: how to determine a “good” sampling rate based on a given filter

I assume that the sampling rate is w_s = 2w_max if we have an ideal low-pass filter that nulls frequencies whose absolute value is higher than that of w_max. Therefore, that the only reason for ...
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2answers
44 views

Notch filter transfer function

For some active filter circuit I have derived the following transfer function: $$T(s) = \frac12\cdot{s^2+{1\over2R_1^2C_1^2}\over s^2+{1\over R_1C_1}s+{1\over2R_1^2C_1^2}}$$ I need to show that this ...
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2answers
245 views

Filtering DC offset of a pulse train

How can I filter a DC offset of a pulse train with an RC circuit? The signal is a pulse jumping between 3.07V and 3.53V. But I need a pulse which is jumping between 0V to 0.5V. How can I filter that ...
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4answers
76 views

Using Differential Amplifier to reduce required RC values

I need to implement a low pass filter to convert a 20kHz square wave into a 20kHz sine wave. It would be nice to be able to use lower values, because in CMOS large resistors and capacitors take up ...
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1answer
47 views

AC Analysis Mindset [closed]

I'm just trying to solidify my foundational knowledge of ac analysis. So when approached with a basic circuit, lets say a RLC circuit, should my first instinct be to convert each group of components ...
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1answer
99 views

RC Filter Circuit Question

Given the image below, we know that the second filter circuit is a Passive Low Pass Filter circuit. I'm assuming it is still a Passive Low Pass Filter with a different corner frequency. Am I correct? ...
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20 views

Is a DSL splitter required, if only a Modem is attached to the line? [migrated]

Annex B is the current standard for digital subscriber line (DSL) in Germany. A DSL-splitter is an analog L-C-filter to separate the POTS (plain old telephone service, like voice and ISDN, FAX) ...
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33 views

Time response of a RC polyphase filter

I'm simulating a circuit using cadence for my master thesis. I'd like to use a RC polyphase filter to get in output a square wave using when the input is a square wave - basically the two wave should ...
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25 views

Suppressing interference in a pressure sensor circuit

I just looked over a circuit designed by my predecessor, which is used to interface with a pressure sensor. It works, but I have some doubts about the way the input filtering is done. The simplified ...
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2answers
140 views

what frequencies do caps filter?

I've been trying to find out what frequencies get filtered out by which type and capacity capacitors, but cannot find simple rules that say "type X, cap Y filters xxx (k/M)Hz - yyy (k/M)Hz". Yet ...
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3answers
106 views

Trying to determine the output of a RC-filter with load

I have a low pass filter like this: simulate this circuit – Schematic created using CircuitLab \$V_{out}\$ is measured right after \$R_1\$, which I suppose means that it is measured over ...
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1answer
140 views

What is the need for the extra resistors in this equalizer circuit?

I am working on a final project for my circuits class to design an audio amplifier. We are creating an equalizer circuit that has passive high pass, low pass, and band pass filters. Every where I ...
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46 views

8th order butterworth frequency response

Ok I'm sure people are getting tired of seeing my filter questions but here's another one. With my new understanding of 2nd order Butterworth filter design I set out to try to design an 8th order. ...
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1answer
74 views

Basic Filter Design

Need help with basic filter design. Firstly there is a low-pass filter(pictured below). I am supposed to derive an expression for the amplitude of the output voltage as a function of \$R_1\$, ...
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1answer
64 views

Op-Amp difference amplifier low-pass filter

I have the following (summing, single supply) difference amplifier circuit: How can I extend this circuit to a 1st or 2nd order low pass filter, with a corner frequency at about 20kHz.
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239 views

Why do we need bulky filters at the input stage of SMPS designs?

I usually see costly and large filters at the input stage of switch mode power supplies. Isn't the AC signal already filtered by the large capacitor (the 100\$\mu\$F one in this example) after the ...
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42 views

Opamp filter cutoff frequency not as expected at higher frequencies

I'm still working on learning Butterworth filters. So far this weekend I went back to school, read about Lapace transforms, poles and zeros, Saleen key design, and finally back to Butterworth filters ...
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1answer
53 views

filter whose gain increases from minimum to maximum for frequency 400Hz to 1kHz

I want to design high pass filter whose gain should increase from minimum to maximum ( minimum upto 400 Hz maximum for 1 kHz) linearly or exponentially. It must be an active filter and my input signal ...
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2answers
54 views

Is the cut-off frequency for each high order butterworth filter the same or different?

From reading I see that I can calculate my cut-off frequency for a given Butterworth filter using the equations below. Let's say then that I have a 8th order filter, and I'm going to make it out of ...
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2answers
75 views

High Order Butterworth Filter Math

I'm trying to learn more about high order filter design, with my goal being to design an 8th order Butterworth lowpass filter in spice, then in the real world. I've been reading a filter book I have ...
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2answers
67 views

How to eliminate 50 Hz noise from amplifier's output

My goal is to amplify signals with a frequency from 100Hz above. My circuit is looking as the picture below. With an oscilloscope, I am trying to measure the output of the amplifier. If the input of ...
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2answers
77 views

Pass DC through (passive) highpass filter?

Background: I'm a student, working on my final year project. I am designing a front end for a software defined radio. We have an IF frequency at 36Mz (and a BW ~8MHz). We are bandpass sampling this ...
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65 views

Relationship between order of filter and impulse response?

I see that the slope of the frequency response of a filter (such as the Elliptic, Butterworth...) becomes steeper as its order increases; for instance, a low pass Elliptic filter with an order of N=3 ...
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451 views

Purpose of 2 resistors in high pass filter?

In the picture below, what is the purpose of R1? Compared to a high pass filter with 1 resistor, how does this affect Fc? Thank you.
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32 views

passive filters in power quality

In power systems,how does cost of passive harmonic filters change with their rating and tuned frequency.This question is for a medium voltage distribution system.
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1answer
58 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 ...
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25 views

Trouble in proteus isis

I need to design a few components in Proteus. Due to complexity of the design ( and size of circuit), I decided to use the sub circuit feature. I made a block diagram of my design and edited its ...
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1answer
80 views

what's the difference between these two low pass filter types

Is there any difference between these two types of lowpass filters? I see the equation is the same, I assume they're both first order then. Just curious if there's any practical difference. Maybe ...
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53 views

LC Low pass filter with high cutoff frequency

I want to design an LC Low pass filter with cutoff frequency of 1000 MHz. the problem is that I want to avoid using low capacitor values, i.e: 3 or 4 pF. My Zo is 100 ohm Any design suggestions ?
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48 views

In the under-damped RLC Circuit, one constant is imaginary, but there can't be imaginary current

I'm just learning about RLC circuits and all the math makes sense, but one thing has been bothering me. In the derivation of the equation for a underdamped, series RLC, the roots to the ...
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3answers
63 views

Linear Phase Response

In many cases it is demanded that the filter has a linear phase response. (like in case of FIR ). Why linear is so important? Why not constant or anything else(any other shape)?
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1answer
94 views

Finiding composition of circuit from frequency response and bode plot

I have the following bode plot and nyquist plot result of an unknown DUT (it is a filter I asume!). I wonder what kind of arrangement it has in terms of being a series or parallel RC or RLC ...
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1answer
101 views

Guitar Pre-Amp stage/filtering and STM32F4

I am currently involved in an academic project which the topic is to design a Digital Tuner for Electric Guitars. My knowledge of electronic is very basic, so here I am. I need to pre-process the ...
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3answers
94 views

RC filter transfer function and gain

For a standard basic RC Filter, the transfer function is as follows: $$ { V_{out} \over V_{in} } = H(j\omega) = { 1 \over 1 + j\omega RC } $$ However, when simulating the circuit, I find the output ...
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3answers
71 views

How can I achieve symmetrical analogue low-pass filtering?

I am experimenting with VCFs for an analogue music synthesiser. Initially I tried a 3-stage low-pass filter based on the sinewave-generator circuit in the LM13700 datasheet but having removed the ...
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1answer
156 views

Comparison of Series and Parallel LC Filters for Noise Reduction

Since there are two basic types of LC circuits that can be used for passing/blocking signals, I'd like to know the differences when using series or parallel LC circuits for noise at a known frequency. ...
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48 views

Transfer function and its magnitude

Can anyone make the transfer function and magnitude of the transfer function more intuitive for me? I understand using them but I feel like there is still a gap in my understanding. I would like to ...
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1answer
79 views

Implementing High Pass Filter in Simulink

I am trying to implement the following block diagram using Simulink in Matlab. I am having trouble getting the high pass filters to work properly. To do the filtering, I am using the First and ...
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1answer
41 views

Is it possible to design cascaded LC filters with inductors sharing the same core?

I want to design an higher order LC filter for filtering out a power signal. In the theoretical design, the inductors are supposed to be on separate cores. But in practice, it will be very costly and ...
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1answer
80 views

Lowpass filter design with transimpedance and difference amplifiers

I have a DDS chip with complementary current outputs that I need to filter. I'm using a design like this: I need a different cutoff frequency, however - 2MHz instead of 50KHz. Note that I'm not ...