Questions tagged [low-pass]

A low-pass filter lets lower frequencies through and blocks or reduces higher frequencies.

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27 views

Amplified Active Low Pass Filter with Capacitor in Place of Resistor

I'm an electrical engineering student learning about OP-Amp circuits, and I ran accross this circuit for an amplified low pass filter. I was wondering how the output of the circuit would be altered ...
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35 views

Frequency of a load curve signal

I have measured a charge and discharge curve of a capacitor with resistor and I want to calculate the frequency of this signal (for a low pass filter). Am I on the right way if I calculate 1 divided ...
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45 views

Electric noise filtering seems not to have any effect over voltage input noise

I have designed two PCBs with slave SPI nodes at both. One of the two PCBs is connected to a Raspberry SPI port, it became the master node. This PCB also has a 74HC51 (suggested for i2c and spi lines ...
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1answer
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Design an electronic circuit, by cascading operational amplifiers and filters, to get the following results [closed]

How to design an electronic circuit, by cascading op-amps, or LPF, and HPF circuits, to get the following results (note: amplifier circuits, which could be used are: inverting, non-inverting, buffer, ...
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1answer
46 views

Low pass filter for ADC signal input

I want to put a low pass filter infront of my ADC. The ADC's sampling rate is 10MHz. I want to sample a signal with a maximum frequency of 50 kHz. So my cutoff frequency for this low pass should be ...
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70 views

Suppress noise on digital signal

Tasked with improving on an existing design, I need to read pulses using a reed sensor excited with a magnet, placed on the front wheels of motorbikes. The system's core has changed, moving from a PIC ...
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2answers
86 views

Sallen-Key Low Pass filter

I was trying to do a project on LT spice for the frequency response for Sallen-Key low Pass filter. But when I tried the Following circuit, I am getting a roll off 20db / decade instead of 40db/decade....
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58 views

How to Filter High Frequency Noise from the Voltage Source on the Input of Control Electronics of Large Machines?

Relevant Background Information As part of my Bachelors Thesis I have to design IOT integrated control Electronics for a Pick-And-Place Machine. This specific machine has modules that can be attached ...
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Capacitor voltage of Buck converter with LC input filter

What will be the voltages across capacitor C1 and inductor L1 in terms of Vg,D,R? From the amp charge balance equation, i1=-io *D because i2=io.From my observation, Vc1= Vg for 0<T<DTs and Vc1= ...
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51 views

Validation of my sinwave converter circuit

I'm pretty green and wonder if I can get my 555 oscillator, H-bridge, low pass LC filter validated. I am afraid it can be very painful making mistakes with such voltages. I plan to use FDA59N30 ...
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37 views

Cutoff frequency of stacked low pass RC filters

How can I determine the cutoff frequency of a filter between V1 and the output marked with the red arrow? All resistors and capacitors have the same value. In the picture is a stack of battery cells (...
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68 views

The transfer function for a 2nd order opamp low pass filter

trying to find the transfer function for a 2nd order opamp low pass filter, can i get a help to find my transfer function ?
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1answer
48 views

Transfer function and weird assumption in circuit

I am new to the concept of transfer function and I have a question that might be somewhat stupid. Given the circuit depicted in the image, we are asked to find the transfer function. According to the ...
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2answers
111 views

DC or average value of a non-sinusoidal signal

I need to find the DC value or the average value of the distorted waveform. First the waveform is given to op-amp voltage follower circuit to prevent it from loading and then to a RC low pass filter, ...
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52 views

Low-pass filter on PDM data provides data that does not have a FFT

I'm trying to convert PDM data into analog form by passing the data through a low-pass filter in Matlab. My approach is fairly simple and matches the answer given in this Electrical Engineering Stack ...
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3answers
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Failed to use a low pass filter in order to convert PWM input to digital output

I want to convert a servo control signal to a digital 5V or 0V output. This is the format of my PWM signal: The different thing is my input pulse width will be either 1ms (minimum) or 2ms (maximum.) ...
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207 views

Trying to implement a digital IIR filter why is this happening?

hope everyone is staying safe. I am trying to implement a digital filter that I made from a continuous transfer function onto a STM32 microcontroller. Using the CMSIS DSP functions found here ...
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I needed to find the minimal order of Chebyshev low pass filter for given dB and rad/s

Is the work ok and which one do I take the smaller value or the bigger one?
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119 views

Output capacitor in buck converter

I am working with the buck converter AOZ1284 Datasheet I want to get 5V with 12V in input so I chose R1=52.3k and R2=10k (Vout = 0.8 x (1+R1/R2) =0.8x(1+52,3k/10k)=4.984V). Also I fixed L=4.7uH. How ...
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395 views

How to do low pass filtering on a differential signal

If I have a differential signal on a pair of wires then how would I do a simple RC low pass filter on this differential signal?
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1answer
90 views

Designing a Chebyshev filter: am I getting the order wrong?

I'm solving the following problem: Consider the design of a Chebyshev lowpass filter with 3 dB DC gain, a passband limited to 1 kHz with a maximum ripple of 3 dB, and a stopband characterized by AS = ...
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1answer
49 views

Bluetooth module resets because of LC filter

I added MH-M18 Bluetooth audio module to my Z906 speakers. Speaker's console has only 3.3V, so I have to use boost converter. For some reason, module outputs 200+Hz noise, no matter what connection ...
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Making subwoofer for car, without amplifier

So, I have these two things and I want to achive a good subwoofer for my car: an 5.1 home theater system with a 20-30w 4ohm subwoofer and a radio player in my car with 4x45w 4ohm output for speakers. ...
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102 views

Voltage regulator before or after LC filter?

When using both an LC filter and voltage regulator to clean up the output from a SMPS, what order should the two elements be in?
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1answer
66 views

CAN Split Termination Capacitor Calculation

I'm trying to use the split termination on a CAN bus, but I'm a bit confused about the calculation for the split termination capacitor. It is described in Figure 10 in the Texas Instruments app note ...
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3answers
101 views

How does load resistance affect RC low pass filter?

I am building a low pass filter. This is the equation I'm using to calculate what frequencies I want to pass though, but I have a couple questions on details. $$ f_c = \frac{1}{2\pi RC} $$ What goes ...
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79 views

Low pass filter target frequency for a mixed signal frequency synthesizer

I'm building a frequency synthesized local oscillator with coarse and fine tuning to span 30.5 to 32MHz. The design follows the following block diagram (bits not essential to this question removed ...
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2answers
98 views

Band-pass filter vs. Serial Low-pass+High-pass filter - Is there a difference?

Is there a difference between a band-pass filter (BPF) and tying a low-pass filter's (LPF) output to the input of a high-pass filter (HPF)? It seems to me that they should do the same thing---or ...
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55 views

How to average output of current sensor to get smooth output?

I am using INA138 current sensor with 100Hz, PWM duty 5%, 8-bit resolution signal load is a resistor, I getting zero readings while actual current readings also appear, edited - zero current sense ...
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1answer
95 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
59 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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223 views

Unable to create proper sine wave with 555 timer

I was trying to create a sine wave with this circuit but with different values. When I just measure the 555 timer, I get a more or less proper square wave: But the moment I add my LC low pass this ...
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1answer
70 views

What is the different bewteen the minimum attenation in butterworth and Chebyshev filter?

I have desgined n of a low-pass butterworth whose specification are fc=1khz , fs=2khz, Amax = 1 db and Amin=40 db. I found that I need to make sure the n gives me larger Amin which = 40db. So I ...
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75 views

Using PWM to create DAC

It is my understanding that a square wave can be converted to a smooth analog signal via passive low pass filter. However, this low pass filter acts like an integrator which ideally achieves the same ...
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1answer
58 views

How to design a low pass filter for Fourier Square Wave

I am trying to create a low pass filter with a cut-off frequency of 100Hz to retrieve a sine wave from a Fourier Square Wave. I am only able to achieve a sine wave with transients. How can I edit my ...
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2answers
87 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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1answer
49 views

I need to design a second order active filter low-pass Rauch structure of Bessel. Design data: f-cut = 15 Hz; C1 = 50 pF. More info in img [closed]

How can I find the values requierd? I tried using the formulas my teacher gave me but c2 is 0 when i use them. Am i doing something wrong? should i use other formulas? I tried to ask the teacher but ...
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2answers
102 views

Low pass filter to remove noise from signal

I am working with an inductive proximity sensor. In the ideal condition, it gives 5V as a high signal when metal is sensed and gives 0 as a low signal when metal is not in proximity. But due to ...
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2answers
26 views

Overall Q of a fourth order LPF and higher order LPF cascaded

If I end up cascading low pass filters to derive higher order filters, how should i calculate the Q of the overall filter? For example if i have the following transfer function $$ H(s)=\frac{1}{(s^2 +...
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3answers
141 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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0answers
18 views

Given a constant R,C, and the input voltage at any time, what is the output of a low pass rc circuit?

In other words, what is the transient response Vo(t) of any arbitrary input signal for a continuous voltage input Vi(t) for a low pass filter? We can make some assumptions: A for any given Vo(t), ...
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73 views

Plotting a bode gain plot with the slope in Excel

I am not an expert in Excel, and therefore, I want to know if there is a way of including the slope (dB/decade) in a bode gain plot in Excel or any free software (that allows to first input the ...
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47 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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2answers
122 views

Help deriving the transfer function of an LC circuit?

I have the LC circuit below. I believe (but I'm not certain) that this is a 3rd order filter. Since there are two capacitors and 1 inductor. The circuit is a passive low pass pi filter. The ...
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5answers
290 views

Why are the theoretical and measured frequency responses off a low pass filter different?

The calculated/theoretical value for the cutoff frequency was different to the measured. What is the reasoning behind this other than measurement errors? It should be noted that this was a simple ...
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3answers
51 views

Demodulation/filtering of a binary signal

I'm simulating an amplitude modulation system on Matlab and have got to filtering the demodulated system. The original data to be sent was a 1x100 set of binary data. Which was then applied to a ...
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2answers
69 views

How to find the cutoff frequency using Simulink (from the scope)?

R=1000 ohm C=0.1uF I need to find the cutoff frequency from the scope and to show it matches the theory \$f= \frac{1}{2pi*RC}\$ In this case it's 1591Hz. How do I measure it?
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1answer
29 views

Help deriving a 2-port representation of an RC filter circuit?

I have the circuit below. Its a basic RC filter circuit with source impedance 50Ω from a signal generator, and load impedance 1MΩ||20pF from an oscilloscope at the output. The input voltage V2 is a ...
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1answer
63 views

What does 'passband phase' and 'stopband phase' mean?

I've been provided with a Bode plot for an RC filter circuit with a cutoff frequency of 10kHz. Im asked to find the stopband and passband phase from the graph. I'm confused how these can be just a ...

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