# Questions tagged [filter]

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

1,856 questions
Filter by
Sorted by
Tagged with
80 views

### Passive bandpass Filter

I'm trying to build a passive bandpass filter with the cutoff frequencies of 0,001Hz and 10Hz. It seems that my signal will allways attenuates and i want to know why.
572 views

### Why would an 8-order LPF switched capacitor have a less steep roll-off curve (MAX7405)?

As as I understand it, a higher order LPF will have a steeper roll-off curve. Something like below would happen if we increase the number of order for the LPF: Normal LPF frequency response curve: ...
51 views

### Confusion regarding terminology [closed]

Originally i asked this question on DSP SE yesterday but untill now couldn't get even a single comment so I am reproducing my question here as bigger audience is available here and also my question ...
51 views

### Why does RC circuit create 180 degree phase shift in current?

I was playing around with capacitors in LTspice today to grasp a better understand of how they shift the phase of voltage and current. I created what would be considered a 1st order filter. See image ...
194 views

### Pi filter with resonance in power supplies

I have recently read in older book (I don’t have it on me, it was from at least 90’s) about LC filter with resonance in chapter about filters in power supplies. It looks like regular pi LC filter but ...
37 views

### Filtering AC Control Signals

I'm having a problem with odd noises in my guitar amp and I'm really struggling to find anything online. Here's a sample of the noise: https://www.dropbox.com/s/z7ggll3q6219l0o/Noise.mp3?dl=0 I've ...
22 views

### LTspice, Sallen & Key low pass filter + Low pass filter order 1

First of all, sorry for my English, it isn't my native language. I want to cascade a first order low pass filter and a low pass Sallen and Key structure in order to get my bandwidth at 30 Hz (Fc = 30 ...
201 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 ...
409 views

### RC-LC network equals lowpass filter of third order?

As far as I know only this are two lowpass filters (R-C1, L-C2) of order 1 and 2 respectively. Is it possible to denote this circuit as Low-pass filter of third order? Or is it possible to transform ...
54 views

### VHDL Comb-filter in decimation

How to implement the following equation in vhdl: Y(n) = X(n) – X(n-4) ? My attempt ...
342 views

### Finding the transfer function of an op amp filter circuit

I have the following third order filter circuit: simulate this circuit – Schematic created using CircuitLab And I know that the transfer function looks like: \mathscr{H}\left(\text{s}\right)=\...
16k views

### How to calculate ripple voltage in this bridge-rectified zener-regulated circuit?

For one of my labs I need to design a power supply with the ripple less than 1% of the nominal 4.7 V value (since Vz = 4.7 V) and calculate its load regulation. I know that the ripple will most ...
70 views

### Why does the dynamic error of a low pass filter decrease when adding a load at the output?

I have this anti-aliasing low pass filter where R = 100Ω and C = 3.62μF. When the input has a frequency of 50Hz, Vin(t) = sin(2π*50t), I have worked out the dynamic error and found that the maximum ...
146 views

### Easiest way to find transfer function of a lossless ladder filter after we finish design?

I have completed my Lossless Ladder BPF design, but I don't know how to find the transfer function of the resulting circuit without going through the slow and rigorous process of getting resistances ...
39 views

### PLC (Power Line Communication) data line coupling to speakers

I have a PLC (Power Line Communication) to provide internet thorugh cable to all rooms. The problem I have is that this internet data is coupled to the speakers. I can hear like a "noise" (...
525 views

### How much is a decade?

Say I have low pass filter (simple circuit while the capacitor is the output.) If I look at the frequency response at the cutoff frequency the gain is -3db. However after that the slope is -20db\...
2k views

### Bridge rectifier: What is the purpose of these two elements?

I found the following circuit in a random video (don't know what it's worth) and have two questions about it. I get that it's a full wave rectifier, and I think I have a decent idea on how it works. ...
113 views

### I am facing a problem while designing a Schmitt trigger circuit

I am applying a Schmitt-trigger to the waveform given in the figure below. . This is a 3.5 volt signal and I want to perform thresholding so I use 1.58 volts as upper threshold and 1.17 volts as lower ...
51 views

### Common mode filtering for three DC lines

I want to filter common mode noise on three DC lines: +5V, GND, -5V at 1A. Why are there so few options for common mode chokes with three lines? What is a good topology for this situation when using ...
175 views

### What's wrong in my low pass filter design?

I use the magnitude of the transfer fuction |H(ω)|=1/sqrt(1+(ωRC)^2) to calculate the wanted output/input ratio at 0.1. I use R=1kohms, C=0.5uF for a 20kHz noise input. Why do I get nearly nothing for ...
24 views

### What is the latency of a n tap transposed direct form fir filter with symmteric coefficients? [closed]

what is the latency in number of clock cycles for this architecture? This an architecture of 12 tap transposed direct form fir filter with symmetric coefficients
57 views

### Can LC filter at the input of the switching regulator cause problem?

The system I designed uses switching power supply Microchip MCP16311 for operation. The problem is that during Run test, which i let the board communicate with other system via Modbus, the ...
1k 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 ...
73 views

### Circuit simulation too slow on LTSpice

My circuit simulation basically would last forever, it's a filter circuit but LTSpice can't run it. any help/insight will be greatly appreciated!
35 views

### Would joining pads of a pi-filter eliminate impedance changes from line to pad? Would it cause problems with alignment during reflow?

This is a 2 part question: Would joining the pads, such as on the lower pi-filter pictured, cause any problems with alignment of the components during reflow soldering? Would joining the pads result ...
205 views

### RF receiver to hear all carriers at once? (to hear electrosmog)

I would like to build "radio ears", a RF receiver that would allow me to experience the RF "smog" around us as sound in my headphones. A more sophisticated version of the cellphone-to-speakers ...
108 views

### Is this a high-pass filter?

I am not very sure about how to completely solve this question. I tried to calculate the equivalent impedance by C and R and got R/(1+jwRC). Then I calculated the transmittance by using the voltage ...
39 views

### Capacitor selection for RC power filtering

I want to design an RC filter to create a constant current supply from a PWM current supply. The background of where I got here is... I'm using a constant current driver LDB-600L to provide constant ...
291 views

### Vdc in ripple factor

V_p(rect) is the rectified unfiltered peak voltage V_r(pp) is the peak-to-peak voltage after filtering by a capacitor Here is a picture: V_r(pp) is given by the expression: Which I have no problem ...
61 views

### Do lead and lag filters have the behavior of high and low pass filters even if the zero and pole used are complex?

Consider the compensation transfer function $\frac{s+z}{s+p}$ so that the inequalities $0<z<p$ and $0<p<z$ correspond to lead and lag compensation respectively. At very low ...
37 views

### How to draw SPL curve for a parametric equalizer?

I want to show (graphically) the Gain/Attenuation vs frequency of a parametric equalizer. This is my circuit: https://sound-au.com/project28.htm The same schematicas as a screenshot: I want to show ...
327 views

### How to calculate voltage ripple in a BLDC filter module?

Hi I need some calculation for my thesis. A found this picture on the internet. My project is almost the same. It's a pi filter for a 3 phase BLDC. The peak current is 60A. It runs from 12V car ...
280 views

### Low Pass Filters and Bode Plot

I'm doing some homework for my circuitry class and I'm stuck. I have to find the value $\frac{V_{in}}{V_{out}}$ of a low pass filter, the schematic of which I have posted below. I got the break ...
24 views

### Why are complex valued zero and pole not used in lead or lag compensation design?

Consider the compensation transfer function $\frac{s+z}{s+p}$ so that the inequalities $0<z<p$ and $0<p<z$ correspond to lead and lag compensation respectively. It can be seen that ...
374 views

### Voltage phase delay

Is there a method of delaying the phase of AC voltages? I ask because if I could somehow create a second identical and overlapping sine wave one quarter cycle ahead of the original AC waveform in a ...
252 views

### Do passive RC filters need ground?

So, after a bit of searching I can't seem to find an answer to this anywhere, at least not in an easy to understand manner. Ok, lets set a scenario, if we have an audio input (in my project it would ...
124 views

### Configuring Frequency Bandwidth and Input Signal for Bandpass filter circuit

How do I set and configure the frequency bandwidth I want the filter to output to a device? I am using a physical passive bandpass filter which I intend to take the signal in and filter it and output ...
1k views

### High pass filter for I2C

I am building a gimbal and passing I2C through sliprings. Right now I have 1.6Vpp spikes at about ~32kHz on the i2c bus. (The spikes are harmonics from motors which are driven at 16~17kHz). The i2c ...
109 views

### Why do common-mode EMI filters lack damping networks?

I've been going through the design of a few different EMI filters, mainly for buck converter inputs. In many cases the leakage inductance of the CM choke can provide enough inductance for the ...
606 views

### Do we always take the corner frequency of a filter at exactly -3dB?

I'm doing some work on filters, but all the references I can find use a 'perfect' gain characteristic, with the trace starting at 0dB. Is the measurement for corner/cutoff frequency always taken at ...
48 views

### Balanced slope detector load impedance

Hello question about FM demodulation here:In a balanced slope detector in class we discussed this picture: How can we connect a load to the output of the Balanced Slope Detector such that it doesn't ...
79 views

### Why does a buffer amplifier change the behaviour of a bandpass filter?

Why does the implementation of a buffer amplifier separating the high-pass and low-pass filter of a bandpass filter affect the transfer function of the bandpass filter? I thought the point of a buffer ...
64 views

### How to find the Nyquist-/sampling frequency of a Sigma-Delta-ADC

I'm looking at the datasheet of an Analog Devices ADC (AD7124-4) and can't understand what is the relevant sampling frequency to use as a basis for calculating the anti aliasing filter. Is the ...
55 views

### Low Pass filter using Parrallel components

I have a PCB design that I need to add a low pass filter. However I can only add components in parallel. It is going to be very difficult to cut the tracks or add components in series. Is there any ...
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 ...
251 views

### Buffer, amplify, filter, sample - In which order?

I'm trying get an audio signal from a high impedance source (guitar or mic) to an ADC. Some casual research suggested that I should filter my signal before amplifying it. My current mental design is:...
164 views

### How to properly step down the voltage of a DC+AC signal that then goes inside a pin of a PIC?

The reason of the question is because i don't know if this is the correct way of regulating a signal that goes inside the pin of a PIC that accepts a signal that goes till 3V3. In the following image ...
180 views

### Simple circuit question: nodal analysis

"simple circuit" I'm trying to find vout as a function of v1,r,c, and v2, but I'm i'm kind of stuck on what to do. I'm pretty sure you need to do nodal analysis, but I've never really encountered a ...