Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [low-pass]

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

1
vote
0answers
28 views

Designing a Band Pass Filter

I need a band pass filter that only accepts frequencies from 1000 to 1400 Hz and then toggles the transistor. It has to work from .1 Vpp to 1 Vpp and rejects anything else. I have been testing this ...
0
votes
0answers
30 views

Second order stable filter for RLC circuit

I have the above circuit which is described by the following differential equation: \${d^2y / dt^2+1/RC*dy/dt = 1/RC*du_1/dt + 1/RC*du_2/dt + 1/LC*u_2} \$ where \$y=V_c\$. What I want to is to ...
0
votes
2answers
132 views

Low Pass Filter Wrong Pole Location

I wanted to understand and derive an equation of simple low pass filter that shows the location of pole in frequency response graph (Bode plot). So, here is the derivation: $$V_{OUT}=\frac{V_{IN}*...
0
votes
1answer
70 views

How to get 50 Hz sine wave from inverter bridge driving PWM pins of MCU

I am using this circuit to see the sine wave coming from a DsPIC Pins to check the shape of sine wave created from my sine table. PWM frequency is 18 kHz But the sine wave does not seem to be ...
2
votes
1answer
56 views

Lowpass Filter and Attenuator

I am designing a circuit to power a brushed DC motor. The motor will be given 24VDC, modulated with PWM. I would like to have an analog voltage sense capability for use with my Atmel ATmega328P @ 3.3 ...
0
votes
1answer
32 views

Problem related to the transfer function of RC low pass filter

I have the following question: For the passive RC low pass filter shown below: $$V_S(t)=\cos(t)+\cos(100t)$$ $$V_0(t)=\alpha\cos(t+\theta)+\beta\cos(100t+\phi)$$ (where \$\alpha\$, \$\beta\...
0
votes
1answer
64 views

Cutoff frequency of a second order low pass RLC circuit

L = 25 mH, R =1 kOhm, C = 10nF and Vs(t)=sin(wt)V, freq = 500 Hz I am trying to calculate the cutoff frequency of a second order low pass RLC circuit I don't know if I can still apply the formula of ...
2
votes
4answers
868 views

Detect ring signal using a low pass filter

I created 2 boards communicating each other like an intercom system. One of them has a button to send a ring signal to the other. The ring signal consists of PWM signals created by an MCU. I want to ...
1
vote
2answers
97 views

High Pass vs Low Pass simple Circuit (RC vs CR)

In an RC circuit, where the resistor comes before the capacitor, the circuit acts like a low pass filter. Whereas in a CR (I don't know if that is how you say it) circuit, where the capacitor comes ...
0
votes
1answer
52 views

Calculating the transfer function of this op-amp circuit

The first op-amp is a differential, second one is a follower and third one is a second order low pass filter. I've been struggling with the low pass and the final output of the circuit and I am not ...
1
vote
0answers
38 views

Physical significance of positive group delay with negative phase delay

This question is an addendum to: Is group delay the same as the delay of a certain frequency? Lately, I've been going back to basics to better understand the concepts of group and phase delay, so I ...
1
vote
3answers
99 views

Using shielded audio cable for potentiometer sensor

I'm trying to measure a potentiometer from an Arduino's ADC. The potentiometer has a maximum value of 100k ohms and is located about 1 meter from the Arduino. The potentiometer's wiper is wired to the ...
0
votes
0answers
71 views

Non-inverting Lowpass Filter with Capacitor in Feedback

I am looking for a circuit that I expected to find everywhere but I don't. The "active" lowpass filter I often see in the web uses an RC filter with a buffer in series. simulate this circuit – ...
0
votes
2answers
211 views

Gibbs phenonemon in real life

If I feed a square wave into a first order, passive, low-pass filter (resistor and capacitor), I get the following results on an oscilloscope (sorry, I don't know how to scale and rotate images): Why ...
0
votes
3answers
92 views

Standard ways to make a variable low pass filter

I tried out a basic low pass filter on one of my analog synthesizers: simulate this circuit – Schematic created using CircuitLab and this seems to work. I was wondering how I can create a ...
0
votes
2answers
57 views

RC Waveform output signal confusion

I've been struggling to understand how filter capacitors specifically low pass filters achieve their output signal waveform. If I take the example from https://www.electronics-tutorials.ws/rc/rc_3....
-1
votes
1answer
47 views

Lpf ramp response intution [closed]

How to intutively draw ramp response of low pass filter intutively . I am able to do it from laplace transform but i am unable to understand..
1
vote
0answers
47 views

How does the data rate of a CAN bus affect the value of the capacitor used in a split termination scheme?

I'm helping to redesign the CAN bus of an electric car, and we're interested in achieving higher data rates of up to 8 Mbit/s. We have a transceiver selected, a CMC to reduce inductively coupled ...
0
votes
3answers
341 views

How to make a low pass filter of current, instead of voltage?

Is there a way to low-pass filter current, rather than voltage? Let's suppose there is a circuit consisting of a current source and a load. The current source may have a little bit of current ...
0
votes
1answer
52 views

LPF and AMP for ADC with op amp not giving sufficient gain

I have a project where I need to have audio input into atmega168PA. I've decided to implement it by using an electret microphone which will feed into op amplifier for low-pass filtering and ...
1
vote
1answer
123 views

Noise problems in current sensing

I have the following circuit: simulate this circuit – Schematic created using CircuitLab I am using a motor from an electric bike, as a generator and I am rotating it using a drill, to test ...
9
votes
2answers
1k views

Low pass filter with two capacitors?

I'm trying to drive a speaker from an ESP8266 for a project, and found an article suggesting (ab)using I2S as a 1-bit Pulse Density Modulation DAC. Apparently that's pretty noisy, so the article gives ...
0
votes
3answers
94 views

What is the time derivative at t=0 for a second order low-pass step response?

For a first order system like an RC filter you have something like $$y(t)=1-e^{-\frac{t}{\tau}}\\ y'(t)=\frac{1}{\tau}e^{-\frac{t}{\tau}}\\ y'(0)=\frac{1}{\tau}$$ But for a second order system there ...
0
votes
1answer
50 views

How to determine the corner frequency needed?

I want to design a second order sallen key low pass filter. I want to attenuate a 100Hz signal to around 10%. I need to use a 2nd order low pass filter. How could I calculate the corner frequency ...
0
votes
1answer
250 views

Transfer function of high pass filter via impulse response function

I'm having a hard time computing the transfer function of a high pass RC filter, by taking the Fourier transform of its impulse response function: $$ H(\omega)=\int_{-\infty}^{\infty} h(t)e^{-i\omega ...
1
vote
1answer
120 views

How to design filter for inverter for following cases?

I am going to make two pure sine inverters for collage project. Both inverter uses 24V battery as DC voltage source. Switched to ~360Vdc and ~180Vd by boost converter accordingly. Both then switched ...
0
votes
2answers
74 views

RC Filter measured response differs from calculated transfer function

I've created a first-order RC filter with R = 68 Ohm, C = 5.0 uF, and I am studying the transfer function of this filter. I have calculated the transfer function to be 1/(1+jwRC), based on the ...
1
vote
1answer
86 views

Change in gain and cutoff frequency of 2nd order passive filters due to amplifier circuit

I'm designing an simple equalizer for a first course in Electric Circuits and having some problems. Circuit diagram and AC Sweep Simulation (Multisim 14): Circuit Diagram AC Sweep Simulation The ...
1
vote
3answers
99 views

Low pas filter time constant for a square input

I am trying to plan a low pass filter as in the picture: I use it to create an ON/OFF lag (Is this the correct term?) I have calculated the time constant τ of the system: My question is: How do ...
0
votes
2answers
361 views

Low pass filter [DELAY]

Ok guys, I can't understand a thing, why a low pass filter will delay only a signal with an high frequency?If I have a RC low pass filter, why the delayed band is only the band that has an high ...
0
votes
2answers
59 views

Natural frequencies of a bandpass filter

I have the following frequency transform used to design a low-pass prototype out of a bandpass specification mask: $$\omega=\frac{\omega_0}{B}\left(\frac{\omega'}{\omega_0}-\frac{\omega_0}{\omega'}\...
1
vote
2answers
315 views

How to calculate the exact delay of a delayed ON/OFF imlemented by low pass filter

I am trying to implement a delayed ON/OFF by using low pass filter implemented by a capacitor and a resistor. I can find the R,C, and cut off frequency by using calculators I found in the internet. ...
3
votes
5answers
737 views

How to calculate the frequency of oscillation of this low-pass phase shift oscillator?

In the following phase-shift oscillator a low pass network is used instead of a high-pass network. simulate this circuit – Schematic created using CircuitLab Usually the frequency of ...
0
votes
1answer
44 views

Turn ratio of an ideal transformer

I am designing a Chevyshev filter of order \$n=2\$, and I the terminant resistances to be equal (since when performing the denormalization of a low-pass circuit for an even order in Chevychev this ...
-2
votes
3answers
143 views

Use of resistance and capacitor in filter

In the band pass circuit what is the role of resistance and capacitors? How do there arrangements don't allow some specific frequencies? band pass filter circuit
0
votes
0answers
52 views

I need to create a switch and low pass filter

The bjt receives a square wave as an input, and at the output(from the low pass filter there should be little to no ripple. to achieve the ripple specs i used a capacitor. on it own the switch works ...
1
vote
3answers
128 views

5th order low pass filter transfer function

It is a complete mystery to me how one would write down the transfer function of a generic 5th order low pass filter. I find it inherently confusing because the question doesn't give any hint or ...
0
votes
1answer
50 views

Instrumentation amplifier with capacitor in the feedback network of the first stage

Instrumentation amplifier with capacitor in the feedback of the first stage. Is this a second order filter or should be analyzed as just first order filter parallel coupled at Rg. Av = 1+2Zf/zg z2= ...
0
votes
2answers
513 views

Transfer function for a Passive Second order Low-pass Filter and to determine the components values

I am working on an assignment about Passive, second order low-pass filters. Cool little things if you get to know them. We are given the placements of the passive components (Inductor(L1), ...
0
votes
2answers
715 views

How to choose a cut-off frequency by interpreting FFT

I have a question concerning low pass filtering of IMU acceleration and gyro data. To choose a reasonable cut-off frequency, I thought about making some observations in the spectrum. Now I have some ...
0
votes
1answer
524 views

calculate the cutoff frequency of a low pass filter

Given that R = 12kΩ and C = 3.3nF, calculate the cutoff frequency (fc), unit in Hz. The frequency response of Vo/Vi is 1/(1+j ω RC). Therefore,cut off radian frequency(Wc) is equal to 1/RC. Then, ...
4
votes
2answers
102 views

Purpose of second resistor in zener-based voltage regulator with low-pass filter

Trying to understand the purpose of the lower resistor R in this example from TAoE The upper resistor R and the capacitor form a low pass filter, but why the lower resistor R? What would change if it ...
1
vote
1answer
84 views

Getting rid of noises after RC low pass filter stage

I am outputting a 40kHz square wave from arduino and passing it through an RC circuit in order to get a clean 40kHz sinusoid out. However, the output wave I am getting is noisy.(see picture) Any ...
0
votes
0answers
56 views

Low-pass filter voltage difference

I did an experiment on a low pass filter, with an op-amp and cutoff frequency of 10 Hz. I was measuring the output voltage when the frequency was less then the cutoff frequency I had 4.18 V with input ...
0
votes
2answers
80 views

Can someone explain how this RFI filter works?

This is an RFI filter from a 12V automotive DC motor. This motor design is over 20 years old and currently in "service" production. We just learned that the capacitor we're using is now in short ...
3
votes
1answer
403 views

Instrumentation amplifier noise amplified

I built a simple circuit with an instrumentation amplifier (PGA204AP) in order to clean a differential signal from noise. The signal is generated few meters away from the acquiring point and the cable ...
0
votes
1answer
347 views

LC-Filter for DPS5005 power supply

I bought a DPS5005 unit in order to setup a cheap power supply. The module seems to be quite popular and has often been described as remarkably good for its low price of about 35 $. However, even ...
1
vote
1answer
85 views

2 pole RC instead of LC filter in Buck

What if I use second order RC filter instead of LC filter in Buck, even it gives roll-off of 40db/decade. Why is LC preferred?
1
vote
1answer
515 views

Critical damping of SMPS LC filter

I am designing a damping resistor [minimum load of SMPS] in parallel to output capacitor of LC filter. SMPS specs: 1. Vout: 200 V 2. Iout [Max]: 2 A 3. PWM frequency: 50 kHz Output filter specs: 1....
0
votes
2answers
170 views

why output of RC low pass filter is ramping up when square wave is applied?

Why am I getting ramping-up voltage at the output of the given circuit below? I should be getting saw-tooth waves right. What am I missing? Output waveforms are like these in LTSpice! Did I chose a ...