Questions tagged [filter]

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

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31 views

Q-factor and Frequency Ranges for EQ

I'm doing a bit of research into some audio graphic equalizers and the following questions have come to mind. Typically, what is the Q-factor for a standard audio graphic EQ/band? For example, if one ...
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1answer
98 views

How to get the DC gain of an active high pass filter?

Edit: I think maybe I am confusing terms (it has been a few years since my last electronics class). I am trying to get the expression for the gain of this active filter amplifier circuit in terms of ...
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1answer
33 views

RLC band stop vs. RC low pass filter for switching noise in DC-DC converter

I'm working with a DC-DC switching IC that has a fixed switching frequency of 10kHz. I'd like to filter out that switching noise. The load is just an instrumentation amplifier, so the peak current ...
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2answers
80 views

Will this photodiode circuit filter this frequency?

I have the following circuit with a photodiode and an LM358P where I intend to blink an LED at around 20kHz. I want to work on it. I have made a calculation through 1/(2piRC), and got something around ...
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2answers
111 views

Unexpected ADC behaviour - can anyone help diagnose?

I'm attempting to read an air temp. sensor made by Amphenol (Datasheet). The sensor outputs is pulse density modulated (PDM) and is filtered to DC using a simple LPF as suggested by the manufactorer. ...
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3answers
2k views

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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2answers
131 views

Capacitive voltage divider frequency response and cut-off frequency

I'm working on designing a guitar pedal based on the topology of an old tube amplifier I own. Between the amplification stages I found an inter-stage filter that I cannot understand in the frequency ...
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85 views

Impossible filter design on bad amplifier

I just recently created this audio amplifier. I built it with real components and it works great. I built it without the "EQ" parts though, since I had not created them yet, so I don't know ...
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2answers
89 views

Finding the cut-off frequency of a filter

For a general filter, what is the way to find the cut-off frequency? In this link Okawa Electronic Design shows a formula for the cut-off frequency of a Sallen-key filter that looks like: $$\text{f}_\...
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3answers
83 views

Breakpoints, poles and zeros of a band reject filter

I'm reading a manual about op. amps. (op amps for everyone) which, at a certain point, speaks about poles and zeros. I'm trying to understand the following example: Given the following band reject ...
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2answers
80 views

Numerical output of RC Circuit

I am trying to numerically generate the output voltage of an RC Filter to that of Plot 1 using the following formula. Using the following code: ...
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1answer
54 views

How to use same low pass filter for square and sine wave

I'm trying to desing simple DDS waveform generator using DDS IC, but I'm a bit lost about designing output filter for it. My requirements are 1 Hz - 25 MHz sine, square and triangle/ramp wave. Using ...
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56 views

LTspice filter giving same output voltage from every input voltage and frequency?

I'm investigating different active filters using LTspice. I've done 3 different circuits of slightly different designs. With each circuit, I use LTspice transient analysis to check the output voltages ...
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66 views

How to select a common mode choke inductance value for power supply EMC filter design?

I would like to know how to select a common mode choke inductance value for EMC filter design for DC -DC power supply The Specifications are : Cutoff frequency : 20 Khz Power suppply Maximum Current : ...
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31 views

Acoustic noise from EMI filter

I am using this proportional valve driving circuit: The valve is 24V, 2W, driven with a 2kHz PWM. I hear an acoustic noise coming from the EMI-Filters L49, L77. I know that the noise is coming from ...
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59 views

Are distributed element filters really distributed?

When looking at distributed filters etched into PCB, I have a hard time understanding why they called distributed. Most of them can be broken into sections and have basically a 1 to 1 correspondence ...
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1answer
50 views

Circuit operation

I have the below input protection and filter circuit. I want to understand how it works. Can someone tell me the purpose of R0101 and D0102 and D0104? As far as my understanding level, when the ...
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1answer
106 views

Damping output filter of buck converter?

Does anybody know if we need to damp the output filter of a buck converter? I came across this paper Passive Power Filters written by R. Künzi. In this paper he suggested an approach to damp the LC ...
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1answer
49 views

How does this T-network op amp function as a boost filter?

Supposedly this circuit is supposed to be a bass frequency booster. I've been using this article as a reference, although the circuit they analyze is a different layout than mine. I apologize if my ...
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33 views

Single balanced mixer, multi-tone analysis

I realized the circuit shown below on ADS. Schematic of the mixer can be shown below. As can be clearly seen from the figure below, to perform a multi-tone analysis RF signal is feeded with two ...
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2answers
67 views

DC accurate low pass filter [closed]

I need to make an dc accurate low pass filter. Actually, I need to measure the dc/average value of a waveform. Suggest me some good and practical 0hz low pass filters. That is, the filter that can ...
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1answer
41 views

Why does adding a gain to a Sallen-key second order HPF change the amplitude response?

As the title suggests, I have done all the necessary calculations to implement a gain into my second order stage of my 6th order high pass filter but for some odd reason, it would change the amplitude ...
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1answer
73 views

How do I calculate the transfer function of this basic terminated RC filter?

I'm reading through an electronics book to teach myself, and I'm in the section about filters. I've been following along so far, but now I'm confused about how the author came to a conclusion in his ...
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2answers
795 views

Why is the output of a high-pass filter not 0 when the input is 0?

I'm trying to design a 5th order Butterworth high-pass filter built on the Sallen-key topology with a cut-off frequency at 100Hz. For some reason, the output has a DC offset of around 5mV when the ...
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1answer
48 views

Which is better for full bridge rectifier circuit? MLCC or Electrolytic? [duplicate]

If I place 100uF multilayer ceramic capacitors at the output of a full-bridge rectifier will there be any problem? Or I need to place electrolytic capacitors? What difference do they make (except size)...
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3answers
104 views

ADC input filter design for DC input signal

My plan is to use an ADS1115 ADC to read a low impedance 0-5V output signal from a level transducer. The ADC data sheet gives guidance for ADC input filtering. This data sheet, and even other input ...
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65 views

Pinball keeps blowing transistor

I've a pinball machine that keeps blowing the transistor for the flipper coil. The flipper coil has a diode across the lugs. This tested good but I replaced it with a new one anyway. Still blows ...
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1answer
62 views

Explanation of filter for op amp controlled MOSFET current sink [closed]

I have designed this circuit and someone suggested R and C to enhance the functionality of the circuit. The circuit is basically a current controlled device. Depending on the voltage set by the ...
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52 views

Generate smooth sine wave from ZYNQ Analog to Digital Converter(ADC)

I have system built on ZYNQ SoC. The ADC of the ZYNQ Soc is fed with 10KHz sine wave and I am getting below wave as the output of ADC. This signal is further processed by further modules. As this ...
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1answer
64 views

What is the stability of a digital signal processed by a filter with z-transform?

I have a question from the book FE Electrical and Computer Review Manual by Michael R. Lindeburg page# DE X-1 with its answer as follows: I tried to solve it as follows: I don't understand why is it ...
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3answers
164 views

ADS1115 ADC input filter - active or passive?

I want to implement an ADC as part of my bachelor's thesis. The datasheet of the ADS1115 show that there is no filtering done by the ADC chip before the multiplexer. As I read here, it is good ...
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1answer
90 views

Inductor - capacitor filter, load disconnected

I'm designing a power supply filter based on inductor - capacitor topology, as shown below. However, when the load is suddenly disconnected, a high current starts flowing through the capacitor, as ...
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1answer
48 views

Fourier coefficient and resolution in simulators

I post below two fourier graphs of the same signal, simulated for two different transient durations: The time domain function is a sine with 60Hz frequency. Transient duration 40ms gives the ...
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1answer
83 views

Is this an Inductor, mystery component 600R/2A?

I was checking a schematic for work, and I saw this component that I don't recognize, marked 600R/2A. Since they are marked L and are used in combination with capacitors, I think they are inductors ...
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31 views

Transformation from Normalized Low-Pass Filter to Denormalized High-Pass Filter

I would like to ask a question about the a method (method number 2) to go from a normalized LPF to a HPF: Note: normalized refers to frequency normalization for the mentioned filters. 1- One method ...
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1answer
73 views

Active highpass filter for microphone, how to choose cutoff frequency?

I am currently taking a class on filter design, and I am learning by doing. I want to make a small project by building a microphone circuit. I found online a tutorial by Great Scott. He made a circuit ...
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1answer
59 views

Trouble understanding an amplifier and filter circuit

First time poster and a beginner at electronics, please tell me if any formatting is wrong. I implemented this amplifier and filter circuit and connected it with a function generator as input to see ...
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2answers
111 views

Finding the cut-off frequency of a filter circuit at -3db from transfer function

I am having issue with finding the cutoff frequency from this filter circuit transfer function as i am stuck at the step shown in the picture attached. I am not sure if i have done the steps correctly ...
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2answers
100 views

Need pointer on designing low pass filter circuit

I am trying to design a low pass circuit for my project which can cutoff frequency of around 300 kHz. Input and output impedance is 50 ohm. The values of R4, C3 which are part of the filter can be ...
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3answers
161 views

Initial Transient Response of Boost Converter

I have been reading about switched-mode DC-DC converters and I'm having some trouble fully understanding the behaviour. Take the following circuit for example (no feedback loop): I understand there ...
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0answers
40 views

Multisim (2008) - How do I provide a reset stimulus using a controlled one shot pulse, in order to properly initialize my design under simulation?

Apologies for the captured image quality but I have a circuit from a communications textbook Fundamentals of Electronic Communication Systems 3rd Edition, by Louis E. Frenzel Jr. The image below ...
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1answer
137 views

Filter w/ seemingly higher output voltage than input?

I'm working on a simple LC filter as part of an AM radio project. I was intending to use a ferrite antenna (modeled roughly by the voltage source in series w/ inductor which is then connected to a ...
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3answers
516 views

Minimizing signal delay when debouncing

I have a mechanical switch that I'd like to use as a signal source for a digital input of a microcontroller. The switch is normally closed, and I'd like to detect the switch being opened as quickly as ...
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2answers
105 views

Why do 2 different online active filter calculators give way different GBW requirements for the same frequency range?

I am confused about 2 different online active filter calculators giving different GBW requirements for the same frequency range. One calculator is giving GBW requirements in the kHz range while the ...
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1answer
44 views

I need help with hairpin filter design. Can anyone help me with the design steps and equations? [closed]

I have the coupled line design. But don't know how to convert it to a hairpin structure.
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41 views

Filtering out a wide PWM

I was doing this project for a kid - an ultrasonic buzzer that alerts you when an object is within 1.7 meters in front of you. We are using an HC-SR04. I set up a 555 in an astable multivibrator ...
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1answer
55 views

How does this notch filter work? [duplicate]

I am trying to learn filters. In the following circuit, the author says that negative and positive feedback are used. I couldn't understand what the circuit parts do. Actually I got the negative ...
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0answers
31 views

How to choose cutoff frequency of an LC filter for an isolated voltage converter?

The manual of B0505S states: "It should also be noted that the inductance and the frequency of the LC filtering network should be staggered with the DC/DC frequency to avoid mutual interference.&...
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3answers
77 views

Why are capacitors high-pass / low pass frequency elements?

I'm trying to study for my intro circuits class final and always found the idea of impedance and filters confusing. Take these two circuits: The first confusion is where are we even measuring the ...
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1answer
75 views

Implementing our own network physical layer for fun (e.g. Ethernet) - is it too difficult? what is the suggested approach?

We are interested in creating our own network stack. For the other layers (application layer ~ link layer), I have done Stanford CS144 and CMU 15-441 so a toy has been implemented. However, I have no ...

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