Questions tagged [filter]

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

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RECOM Input/Output Filter Calculations

I am new to dc/dc converters and was hoping for some input from the community to see if I am on the right track. I two questions with the first being related to the data sheet EMI filters and the 2nd ...
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38 views

DAC Signal Clipped By DC Voltage Source

I'm using a TI F28379D to generate a sinusoidal waveform from a DAC channel. The output of the DAC is shown in Figure 1 with a Vpp of 688mV. This signal is then connected to a resistive network of 1k ...
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design an LC filter for a variable load

I'm working on a single phase inverter, and i'm trying to add an LC filter to get a nice sin curve with a THD < 5%. my problem is that when i test some random values i can get i good THD ..etc but ...
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46 views

Placing an RLC input filter at the input of a buck

Since bucks have current spikes at the input side, it's best to use an input filter as you get better noise reduction than using an output filter (afaik). Using a regulator IC however, that is, one ...
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28 views

Power supply filtering RCL-filter vs alternatives (for LF-RFID driver)

simulate this circuit – Schematic created using CircuitLab This schematic is the manufacturers dev-board design for the RFID-IC power Supply, using a large power inductor at 4A I_RMS and 22uH. ...
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58 views

Pi filter design for SMPS output ripple

Given a circuit like a buck-converter like the AOZ1284PI in a circuit such as this one: Or push-pull converters such as this one: If one was to design at the output a low-pass PI filter with a ...
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Output filter (pi filter) EAGLE design

I am working on a project of wireless power transfer system for EVs. On the secondary side there is a full-wave rectifier which output current charges the battery. Of course, after the rectifier stage ...
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29 views

Charge Injection in Charge Pumps

let's consider the following charge pump, which is used a lot in some PLL circuits (reference): Let's focus on the left part of the circuit (until the Loop Filter Network): its aim is simply that of ...
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1answer
24 views

MOS circuit for RC circuit power

I am currently working on a circuit where we read the time it takes for a capacitor to charge depending on the load. I would like to know what is the purpose of the first stage with Q1 and Q2. I also ...
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Whats the difference in these 2 input filter dampers?

Hi Im designing input filter for tps54202, with input 12V, output 3.3V at 0.5A. To pass emission test I need input filter, L+C should be good for that, but Ive read that its good to add damper to get ...
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51 views

Suitable resistance values for an analog IC

I was reading a chapter of the book "Continuous-Time Active Filter Design" about analog filters design. Let's consider the following band - pass filter, in which its inductances may be simulated with ...
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2answers
88 views

LC filter before analog pin of microcontroller

I am measuring analog DC voltage at the analog pin of dspic33 series microcontroller. The source of the signal is AC. So, I rectified it with diodes and amplify it with op-amps. In order to reduce the ...
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126 views

Why does the capacitor need to be small in RC filter circuits?

Hi there, in this example, it mentions that "One should choose R2 to be as close to 100kohm (to make the C2 small)". My question is: what are the reasons for C2 to be small? Other than the fact that ...
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50 views

Controlling brushed motor speed with variable load with a PWM

I am considering driving a brushed motor driver with an H-bridge and PWM. I'd like to roughly control the motor speed regardless of the motor's load (envision a small robot climbing/descending hills). ...
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40 views

help with simple thevenin circuit and filter

I was trying to solve these excercises with thevnin circuits and filters but I really don't know what to do, could anybody help me?
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How to know whether filter is stable given in- and output shapes?

I have this filter with $$H(z) = \frac1{0.5z^{-1}}$$ How can I know whether this filter is stable given that \$x(n) = a^nU(n)\$ and \$y(n) = -a^n U(-n-1)\$?
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56 views

how to design a low pass filter for square waveform

I have square wave signal of 100KHz with few high frequency ringing from 555 timer.when i tried to use a 100KHz first order rc low pass filter,i got a sawtooth waveform because the 100KHz square will ...
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ac analysis of circuit in LTspice [closed]

I want to AC analysis of circuit , where source is modulate which is going to generate AC signal of varying frequecy and varying amplitude according to V1(frequecy) and V2(amplitude) with respect to ...
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82 views

Gaussian filter circuit

I want to convert a 10 MHz train of square wave, 3.3 V to a Gaussian pulse train of the same frequency and amplitude. This Gaussian pulse will be sent into an electro-optical modulator where it ...
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1answer
58 views

3-dB frequency of cascaded opamps

We have two identical opamps with a first order low-pass response. They both have the same 3-dB frequency \$f_1\$. I need to show that their combined 3-dB frequency (when they are put in cascade) is: ...
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69 views

Notch filter on STM32 Microcontrollers

I need implement real time notch filter to 50 HZ powerline noise My MCU is stm32h753bi , how to do that? is it rationale to do that in MCU or I should that on PC side? thank you
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56 views

Determining values to convert square wave to sine wave at low frequency

For a project I am working on, I have a 1Hz square wave coming from a real time clock, and need to convert it into a sinusoidal wave to pulse LEDs. After some googling and playing around with ...
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174 views

Is it possible to sweep 20 Hz to 20 kHz with one potentiometer?

I'm designing a resonant filter based on a state variable filter topology with sweepable frequency and variable resonance. The filter is designed to sweep from roughly 20 Hz up to 20 kHz (50 kohm ...
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Filters in cascade

Let´s say that in order to avoid having a filter of too large of a degree, I use multiple filters in cascade: Low frequency gain of 8dB Cut-off frequency of 4Hz Chebyshev of order 2 Would the ...
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Conservation of Power in Filters

I have a simple doubt about the conservation of power in systems that include some filters. Let's consider this general situation: The filter is able to attenuate some components (of certain ...
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125 views

Filters generate output even if they are not connected to any signal and does respond differently to different signal sources

opAmps are fed by +/- 9V. I have two more filters like this one, in total three filters. If I use a signal generator as input signal and observe output via an oscilloscope; all those filters give me ...
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118 views

Full wave rectifier with inductor filter

The capacitor-only bridge rectifier can't remove the ripple under heavy load and for a linear lab power supply I need to have an output without any ripple under load. after simulating the bridge ...
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66 views

Prerequisites to learning Passive and Active Filter Design

I am sorry for this as its not really a "question" per se. I am keen to learn analog filter design. So what prerequisites am I looking at before I start self studying myself about analog filter design?...
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143 views

Need help designing and implementing an op-amp based distortion circuit

I've been attempting to design a distortion pedal for use with my bass guitar and amplifier. The simulations in LTspice were promising, I moved to implement it and, in short, it did not work. Note: ...
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90 views

Substitute for 455 kHz Ceramic filters in new designs

I was wondering what has ever happened with the 455 kHz ceramic filters commonly used in the second IF stage of a superhet radio receivers? All but just a very few (and those left over don't seem to ...
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1answer
49 views

Equivalent model of my (real) transformer

I have created a transformer using a small cylinder (a tube) made of ferrite. The primary coil has \$N_{1}=5\$ turns of coil wire, while the secondary \$N_{2}=50\$ turns. According to a recent ...
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adding rc filter to cheap sub

I bought a cheap computer Sub to repurpose it as a selfmade gaming vest. The circuit has 2 amplifiers on it, one for the normal unfiltered sound that goes to the 2 speakers, and then the output of ...
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47 views

Equivalent circuit of a simple transformer?

EDIT: My question is: How can you translate the first circuit into one that uses simple (linear) electrical elements and, as a result, can be solved using mostly Kirchhoff's laws? I am trying to ...
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134 views

Which resistors control the gain of this filter?

Update2: Nevermind the update1, question went far beyond its scope. Accepted answer was my expectation. Update1: I have the filter(bandpass) design below, created using texas instruments filter ...
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76 views

Filter only with capacitor

I have some questions about capacitor and the circuit shown below: The original signal including noise is shown below: There are three waveforms shown in one picture. The top one, middle one, and ...
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66 views

Application of Frequency Response Theorem in Linear Circuits

One of the most important results of control theory for linear systems is the so called "Frequency Response Theorem" (here the references): Briefly, it says that under the hypotesis of stability and ...
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1answer
80 views

Synthesizing this simple analog notch filter?

I want to synthesize this simple analog audio filter which is a notch: The inductor with resistor creates a simple one-pole low pass filter with the cutoff frequency at: fc = 1/(2pi L R) The ...
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1answer
188 views

Class D amplifier question

I am designing a class D amplifier for a pair of bookshelf speakers (Sony SS-MB150H). I guess inside each speaker there is a crossover for each driver but... am I right to assume that I just need to ...
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50 views

Active RC filters

I was reading paragraph 4.2 of this book about Active RC filters. It says that if we want to get a band pass filter with high selectivity (i.e. high quality factor Q) we should use resonant circuits (...
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2answers
87 views

Low-pass cutoff frequency definition (-3dB vs. filter design)

For low-pass filters, we usually define the cutoff frequency as the frequency at which the gain drops by -3dB. Another definition, however, comes up in filter design as one of the parameters that ...
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60 views

Why is feeder network so long and other questions?

I have an mBed Lora 915Mhz shield I attached to a Raspberry Pi. I had some questions about the feeder network. In the attached schematic. Why isn't a simple cap/inductor pair sufficient for an ...
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1answer
35 views

Linear Circuits - Erroneous first order gain observation

At uni, I carried out some lab observations involving a CR circuit (4V AC power source, capacitor, resistor in series, in than order) with the following parameters: simulate this circuit – ...
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1answer
30 views

What is “tap line”?

I am reading this article (https://arxiv.org/ftp/arxiv/papers/1901/1901.02069.pdf) where I have come across this sentence: "we first designed a parallel coupled Chebyshev bandpass filter as shown in ...
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72 views

2nd order Low-Pass Output Impedance and Phase difference

I am trying to calculate the output filter impedance and the phase difference of the inverter that I am designing. However not sure how to construct a formula for both the output impedance and phase ...
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3answers
66 views

Design of second order low pass filter using passive RC components and opamp

I have an RC low pass filter connected to the non inverting terminal of the opamp. There is a feedback resistor from output of opamp to its inverting pin.Then an RC low pass filter is placed at the ...
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1answer
69 views

How can I find the origin of equation about this filter circuit?

Probably everything is clear for anyone but I can't still understand how can the author found the Vo equation for this circuit. I hope somebody in here will show me the way.
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1answer
66 views

Passive bandpass filter simulation gives wrong cutoff values

I'm simulating the following passive bandpass filter in LTSPICE, and can't figure out why my calculated cutoff values don't match the -3db values in the simulation. Here's the circuit I'm simulating: ...
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112 views

All Pass Filter

Consider the next transfer function: $$H(z) = \frac{b+z^{-1}}{1-az^{-1}}$$ where \$a\$ is a real number and \$|a| < 1\$. My intention is to make an all pass filter, for that I need to determine ...
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51 views

Trouble designing a low pass filter

I was trying to design a simple 3rd order low pass filter by cascading 3 first order low pass filters along with an amplifier at the end. The transfer function is straightforward: $$ H(j\omega )=4\...
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1answer
83 views

How can I calculate the amplitudes of this signal's harmonics?

How can I calculate the amplitude's of the harmonics? This signal is the voltage of a capacitor bank. There is a few amperes of current on the capacitors in form of PWM. On the signal the 200mV Jumps ...

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