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

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a question about gain equation of low pass filter

This webpage says: For a passive low pass filter, The gain equation is the RC potential divider equation: Here, They say: The frequency response of the circuit will be the same as that for the ...
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20 views

Post amplification filtering

I'm trying to construct a guitar cabinet, and currently have an odd setup. Here's a visual: http://postimg.org/image/g6nl0zuq9/ The circuit is: Amplifier(+)->S1 S1->S2->S4->Amplifier(-) ...
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1answer
45 views

How to design a suitable low pass filter for different waveform

I want to realize a DDS signal generator based on FPGA,which is composed of FPGA,DAC and low pass filter,and the FPGA control a DAC to output different kind of signal. Here are the system performance ...
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2answers
39 views

Anti-aliasing filter as notch and lowpass

In order to reach a steep attenuation for an analog antialiasing filter, there are issues if a high Q notch filter is followed by a low order lowpass filter (or vice versa)? The notch resonance could ...
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3answers
78 views

Help with low-pass filter and TTL logic interface

I am working with a motor control board which controls a DC motor (speed and direction). This board uses two SPDT relays for direction, and some sort of PWM for speed. Here's an abbreviated ...
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1answer
62 views

Low pass filter in the input of ADC supply

Attached figure shows a LPF connected to the input of an ADC preset in the microcontroller. Can anyone please explain why an inductor is connected in parallel with the resistor. Regards Hari
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1answer
49 views

Low pass filter on PSU and target amplifier

we are designing a LLC resonator PSU to feed a class D amp The switching frequency of the LLC PSU is 80-140Khz. At the end of the PSU we are thinking to add a LPF ( PI filter ) with a cutoff ...
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2answers
72 views

What sort of graph of Vout/Vin vs frequency will a low-pass and high pass filters have?

The graphic is in log (Vout/Vin) vs log (f). I think that, for the first one, would be something like this: http://www.sosmath.com/algebra/logs/log4/log42/gl02.gif and for the second one will be the ...
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1answer
44 views

Measuring the electrical performance of a low pass filter

I built a portion of a loudspeaker crossover circuit. Specifically, a simple 1-st order RC low pass filter. The filter is designed as shown on this page here. The Resistor is 15.5 Ohms The capacitor ...
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2answers
71 views

Does a sound card low pass filter input?

I ask this question just because I'm curious to find out. As far as I understand, the Nyquist theorem says that the sampling frequency must be at least twice the bandwidth of the signal to be ...
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1answer
70 views

Lowpass LC filter

Here is my task: Lowpass filter circuit is given: Input signal to this circuit is: (it's periodic signal) L=36.4mH, C=85.4nF. Calculate and draw output signal. My idea is to: 1) Represent ...
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1answer
42 views

LC Filter Attenuation

Hi I built a simple LC low pass filter and I supply it with a 1 volt peak to peak ac voltage at 200 Hz from a function generator. My cutoff is set at 700 Hz and I have selected my circuit components ...
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1answer
115 views

Practical Opamp integrator problem

The opamp has an unity gain of 1 MHz.So when the resistor in parallel acts a feedback to bias the opamp stable.So if not for the capacitor,the circuit would have been a inverting amplifier with ...
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2answers
69 views

Inverse Filter Circuit

I have calculated the inverse transfer function of a low pass filter, and was wanting to design a circuit so that the original filters effect will be cancelled by its inverse. What would be the most ...
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1answer
179 views

PWM (Pulse Width Modulation) vs DAC (Digital Analog Convertor)

I am working on a project where I take over the control of a Nintendo 3DS Touch Screen. The touch screen is a 4 pin system. I have it all wired up and working, however I cannot get the screen to ...
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1answer
54 views

Inverter with low pass filter?

Is this low pass filter (see the part marked in red below)? If yes, why author used low pass filter in this place?
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1answer
129 views

on-chip low-pass filter with sub-Hertz cutoff frequency

Sometime ago I had to implement an on-chip (CMOS 65nm) low-pass filter (first order) with very low cutoff frequency (lower than 100mHz). I used PMOS pseudo resistors and momcap, and had to check all ...
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0answers
62 views

Need help increasing rolloff for low pass voltage controlled filter

I am doing an LTspice simulation of this circuit (using LM13700) but with one difference. The power supply is +-5V. Also, by varying the control voltage, the cut-off needs to be able to be varied. The ...
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3answers
130 views

Second order RLC filter and load resistance choice

In this 2nd order, low-pass filter circuit simulate this circuit – Schematic created using CircuitLab I am interested in the transfer function $$ H(s) = V_L (s) / V_g (s) $$ which is ...
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0answers
85 views

Guidance designing low-pass filter for audio circuit power supply

I'm developing a BeagleBone Black cape that has, among other things, and audio CODEC and 10 W amplifier. The “other things” include a connection to WS2812 LEDs, which generate a lot of PWM switching ...
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0answers
80 views

Remove power line hum and noise from DC source

We are testing our device in a local RF compliance center next week. I spoke with them on the phone and they suggested using a car battery instead of an AC powered DC supply. The reason they gave ...
11
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4answers
970 views

Why don't decoupling/bypass capacitors need resistors to perform their function, like regular filters?

Why don't decoupling/bypass capacitors need resistors to perform their function, like regular filters? Is it because the stray resistance of copper traces is enough to filter, along with the ...
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0answers
86 views

Trouble with decoupling capacitor on simple low-pass circuit

I'm trying to filter all signals above ~350Hz from an electret condenser microphone's output and amplify what's left for analog input / DSP. I'm a beginner, so I cobbled together the design from a few ...
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2answers
215 views

How to measure cutoff frequency of a low pass audio filter?

I've built a low pass filter for use in a synthesizer and would like to measure the cutoff frequency compared with various different control voltages to profile its characteristic. I have access to a ...
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1answer
173 views

Low Pass Filter For Square Wave Through An Optoisolator

I've got a higher voltage square wave input that I'm feeding through FOD817B Optoisolator. The square wave frequency is in the range of 30 to 300 Hz. The Circuit is like this: simulate this ...
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2answers
169 views

Matlab low pass filter design -removing noise

I am designing a low pass filter in matlab to remove the noises shown in the image. The original signal of interest lasts only for about 80 ms and rest of the signal are noises from probe tip. In ...
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3answers
392 views

DSP Cutoff vs Sampling frequency question on low pass filter

Is it unrealistic to have a 125 MHz sampling rate with a cutoff frequency of 5 Hz? I downloaded a few filter programs and used their methods and it seems that even with thousands of taps it still ...
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1answer
43 views

What are these things called in a bode plot

Here is a low pass filter bode plot: In the bode plot theory, what is K called? What is ω0 called? What do these two represent for a low pass filter? Does K not represent an amplification or ...
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1answer
289 views

Low-Pass filter on AVcc pin for ATtiny

The datasheet for the ATtiny861a states that "If the ADC is used AVCC should be connected to VCC through a low-pass filter". The datasheet doesn't specify what values I should use or what style of ...
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1answer
80 views

What to do with the Balance and NC pins?

For a course project, we are to use an LF356 operational amplifier What does the Balance and NC do? and I do not think I need it for my project(Sallen-kay filter 4-pole). Do I just ground it?
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2answers
582 views

Obtain an accurate DC value in an AC+DC signal

Background: My goal is to use an Arduino with two proximity probe sensors to achieve some output. It is worth mentioning that the output of the proximity probe has two components: DC output that ...
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1answer
48 views

Dual passive low-pass filter

I am building a class D amplifier and need to design passive low-pass filters for H-bridge with cut off frequencies at about 400 Hz. However, I am unsure about few things, this is the simplified ...
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1answer
131 views

Digital Low-Pass Filter When Oversampling Audio

The human ear can hear sounds up to ~ 20KHz. Some ADC's oversample. For example, to capture frequencies up to 20KHz, an ADC converter might sample at 160KHz. The steps are: 1. Filter the audio with ...
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1answer
69 views

Current regulator with controller?

I want to implement a circuit which allows to regulate the current flowing to the load. I have two use cases: Case 1 is the normal case where I would set the max. allowed current with a ...
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1answer
119 views

Filtering noise off of PWM signal

I am trying to measure the resistance of a nichrome wire that has a PWM (1000Hz and different duty cycles between 0 and 100%) voltage applied to it from a 5.0V regulator. The setup I have in mind ...
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1answer
358 views

EEG amplifier circuit low and high pass filters. Oscillations, noise, etc

I designed a EEG amplifier circuit for for EEG signal amplification and filtering. Because I never had any experience in filters, It would be highly appreciated if someone could check my design. In ...
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1answer
172 views

Low Pass Filter calculation

I am designing a circuit which reads a analog signal(DC - Response from a photo-diode exposed to tungsten lamp) to a 12 bit ADC. The ADC is MCP3202 running at 1Mhz speed and uses 16 input bits to get ...
2
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1answer
422 views

Input impedance of PIC32 ADC pin

I want to measure temperature of an oven using a thermocouple. The maximum change in the temperature will be 1oC/s. The amplifier section will already contain a low pass filter, but I want to put an ...
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3answers
223 views

Which low pass frequency filter to configure to measure/calculate DC-DC converter efficiency?

I am measuring the DC-DC converter active power (P in watts) efficiency of a TI (Webench) LM3150 PCB that converts 12 to 5VDC. In the answer of question Measuring precisely the efficiency of a power ...
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2answers
254 views

Low-pass filter for high power application

I'm designing a LP filter that should be used for a load of up to 2000W. I want to filter the AC voltage that supplies a controlled heater which uses a TRIAC for control. I've tried one approach but ...
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1answer
154 views

RC low pass filter PCB layout limitation

I have an RC low pass filter for debouncing a GPIO pin. Do I have to place the resistor and the capacitor close to each other? Currently the capacitor is near the GPIO pin, and the resistor can be ...
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1answer
185 views

Help understanding 60 Hz low pass filter behavior in oscilloscope

I have been testing this circuit in simulation which is supposed to be a low pass 60Hz filter, as far as i am concerned the simulation works as intended in simulation starts filtering frequencies ...
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2answers
1k views

Should I always put a low-pass filter on an ADC input?

I'm a recent hobbyist EE and new to micro controllers. I've built a test circuit to make measurements with a type K thermocouple, a PT1000 as well as an oxygen sensor. The weak signals go through a ...
2
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1answer
93 views

Transfer function of a cascaded passive + active filter

How do I get my H(s) transfer function from this circuit? If there was infinite impedance between the two filters, I'd just do H_LP (s) * H_HP (s). However, we are assuming that the input/output ...
4
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2answers
310 views

What is the steepest roll-off achievable for an analogue low-pass constructed with a single op-amp?

I was wondering about this question. What if the only design requirement is having the highest steepness of the roll-off but using only one op-amp? I know it's possible to construct approximations of ...
2
votes
2answers
377 views

Calculating SNR after lowpass filtering

I am currently working with a sinusoidal signal buried in noise. I filter the signal with a low-pass filter of which I know the transfer function. How can I calculate the SNR after the filtering ...
3
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3answers
325 views

Tool to calculate cascaded but independent single-pole RC hi-pass filters

I frequently use a single op-amp stage for both gain and hi-pass filtering. I normally implement 2 independent single-pole low-pass filters: the input to the op-amp and the ground end of the ...
4
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1answer
102 views

For IIR low-pass filters, what design provides the least amount of phase shift in the pass band?

Given all the possible design options for IIR filters one could consider (e.g. Butterworth, Chebychev, inverse Chebychev, elliptic, Bessel, etc.) which design provides the least amount of phase shift ...
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1answer
131 views

Transfer function of a R+RLC low pass filter

Here's a picture of the R+RLC circuit: I'm trying to find the frequency response of this low pass filter, my solution is below and please let me know if there is anything wrong with it. My ...
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4answers
504 views

Low pass filter issue - is the 10k resistor part of the circuit?

This may be a really simple question but Op Amps still confuse me a little. I have a low pass filter circuit as shown below. My question is whether the 10k resistor is part of the filter circuit ...