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

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143 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
33 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
46 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
53 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
42 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
115 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 ...
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1answer
35 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 ...
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2answers
272 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
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2answers
46 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 ...
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3answers
103 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 ...
3
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1answer
50 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
74 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
418 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 ...
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1answer
62 views

Transfer Function Of Multiple Feedback Filter - with a difference!

I posted a question yesterday about a circuit i thought was a low pass filter, however it turns out to be a transimpedance amplifier and a 2nd order low pass filter all in one! The input signal is a ...
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0answers
61 views

Op Amp Low Pass Filter - Feedback not connected as expected?

I have come across a circuit which I think is an active low pass filter, but it seems to have a few differences from the standard circuit I am used to seeing. Referring to the schematic, I am not ...
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2answers
105 views

Class D amplifier woofer filter designs

I am working on a 140W class D amplifier for my subwoofer. I am familiar with its topology but have few questions. The music source is a radio that ouputs 200mV peak-to-peak signal containing all ...
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1answer
84 views

Low Pass Filter With Hall Effect and ADC Help

Background: I am using the Allegro ACS758KCB-150U hall effect based current sensor, here is the datasheet, I am using it to measure current drawn by 24V motors, between about 20A - 130A. The reason ...
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3answers
216 views

Analog preprocessing circuit (anti-alias/pre-amp) for driving ADC

Background Similarly to what Jeri Ellsworth did in her C64 Bass Guitar hack I am working on an audio-to-midi converter for my bass guitar. I am also planning to use piezo discs as sensors placed ...
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2answers
91 views

LM358 Single Supply problem

I am trying to build a low pass filter circuit from the LM358 datasheet from TI. Looking at the pinout and building the circuit I cannot get something basic like this filter to work. I have everything ...
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3answers
127 views

Trying to determine the output of a RC-filter with load

I have a low pass filter like this: simulate this circuit – Schematic created using CircuitLab \$V_{out}\$ is measured right after \$R_1\$, which I suppose means that it is measured over ...
4
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1answer
116 views

Basic Filter Design

Need help with basic filter design. Firstly there is a low-pass filter(pictured below). I am supposed to derive an expression for the amplitude of the output voltage as a function of \$R_1\$, ...
2
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1answer
94 views

Op-Amp difference amplifier low-pass filter

I have the following (summing, single supply) difference amplifier circuit: How can I extend this circuit to a 1st or 2nd order low pass filter, with a corner frequency at about 20kHz.
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3answers
109 views

How can I achieve symmetrical analogue low-pass filtering?

I am experimenting with VCFs for an analogue music synthesiser. Initially I tried a 3-stage low-pass filter based on the sinewave-generator circuit in the LM13700 datasheet but having removed the ...
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2answers
552 views

A simple RL circuit, getting transfer function, matching with results

I'm doing little lab exercise with an RL circuit. I need to check if I did this analysis right, because the numbers I got and the numbers that should theoretically be there are so far off, I figured ...
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2answers
233 views

What happens to a DSB signal if I use an envelope detector instead of Low Pass Filter

What happens to a DSB signal Modulated signal if I use an envelope detector instead of Low Pass Filter ? I am interested in knowing how the output signals vary in case of a envelope detector. I know ...
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68 views

Singnals, filters and power output

I have couple of questions: A square signal goes through a low pass filter and in the output of a circuit we get a sine. What happens there? Give a scheme? This is really weird, because, from what ...
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1answer
53 views

Input to amplifier with LPF not working

I am trying to build a pink noise machine to use at work. See schematic below. If I connect the output from the MM5837N (noise generator), directly to the amp circuit. It works fine, and is nice ...
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1answer
152 views

Low-pass filter for digital input

I made a digital input circuit to convert a 120Vac waveform into a digital 2.3V signal. I would like to add a "low-pass" filter at the output to get a low level for higher frequencies than 1kHz. I ...
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2answers
292 views

Reducing Ripple in the Zener Regulator

In the Art of Electronics (Horowitz & Hill) the following circuit is given as a solution to reduce ripple current caused be variations in input voltage (pg. \$ 69 \$): "An alternative method ...
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1answer
144 views

Low pass filter value for DAC

I was wondering, how to calculate the values needed for LC/RC filter when using it for digital to analog conversion? Also, how does the square waves frequency affect DAC ? For example: lets say I ...
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2answers
79 views

Why would an 8-order LPF switched capacitor has a least steep roll-off curve (max7405)?

As far for my understanding, 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 ...
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2answers
190 views

Variable Voltage Using PWM and Low Pass Filter

I am trying to control a steady DC output voltage using a Micro controller with a PWM duty cycle. With the current schematic, the Voltage on Vout is pulsing along ...
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2answers
610 views

What do you mean by -3db cut off frequency in low-pass-filters?

I have a low pass filter as follows. simulate this circuit – Schematic created using CircuitLab Using voltage divider I get $$\frac{V_{out}}{V_{in}} = \frac{1}{\sqrt{1+(\omega RC)^2}} ...
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1answer
166 views

What Load impedance to use for LC Filter before transformer?

I have an inverter circuit in which I want to filter the output with an LC filter. Lets say the fundamental component that I want is 60Hz. When designing a Low Pass LC filter, I need to use the load ...
2
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1answer
268 views

How to build LED dimmer for room illumination - PWM, low pass filter?

I want to illuminate a room. This will be done by two LED strips 60led/m, each 5m long, located along the tops of opposite walls. In order to get full light power, they together consume 4A@12V. ...
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2answers
85 views

Cascading Low Pass Filter Parameters

I'm trying to implement two cascaded low pass filters in a software application so that I can smooth out a potentially volatile data set. Based on the incoming data, I want a signal to be turned ...
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0answers
105 views

8 IR sensors and 74HC4051 multiplexer where to place low pass RC filter?

So I've got 8 IR sensors like these Then I connect them to multiplexer. And arduino will run mux's selectors through the loop.. Something about 5-10 times per second(read every sensor 5-10 times ...
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2answers
128 views

How can I keep my sinusoid in phase with its input after filtering?

A section of a circuit I'm working with makes a sinusoid from a square wave by passing it through an 8th order filter (MAX293). Up until now, everything was ok, but I was told recently that the input ...
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2answers
2k views

How to design a 4th/6th/8th passive low pass filter?

I am trying to design a 4th/6th/8th passive low pass filter. The filter is used after a DAC to generate a fixed frequency sine wave. The DAC will export a square wave at 1kHz. So the pass band of the ...
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3answers
211 views

LPF (low pass filter)

If I have for example DC signal (voltage and current) and I select on my "scopecorde/datalogger" LPF (low pass filter, not digital! with 5 Hz) what happened on output signals? Is that the same as ...
2
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1answer
88 views

Using PWM to generate analog output

I am trying to understand this application note from Microchip about using PWM and a low pass filter to generate an analog output. I have a few questions regarding to the article: In the example ...
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2answers
206 views

Reducing jitter and improving speed of accelerometer output

I'm not sure if this is an EE question or a StackExchange question due to the programming involved, but anyway here goes: I just built a tilt sensor for my tractor's front loader. I wanted something ...
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3answers
119 views

Circuit analysis of active LP-filter with 2 OP amps

So this is our diagram: We want to find C1, C2, R1, R2 so that our frequency cut-off is 1kHz. We also need to have R2C2 = 2 * R1C1. So, my first instinct is to: Use KCL nodal analysis Set C1 ...
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3answers
1k views

Time delay: digital low pass filter VS analog low pass filter

I am new on digital filter, hopefully I can get some intuitive insights here. So, here is the question: A low pass filter with 5Hz cut-off frequency is to be designed. The signals presented have ...
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3answers
162 views

Current source - Achieving a defined settling time with variable load resistance

I'm trying to build a voltage-controlled current source which is supposed to work with a wide range of load resistances. Currently the plan is to use an NPN transisitor as voltage follower to do the ...
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1answer
59 views

The bandwidth Ω of a low-pass signal f(t) ↔ F(ω)

I'm not sure about the answers to the two parts of this question: The bandwidth Ω of a low-pass signal f(t) ↔ F(ω) is defined by the constraint: $$ \frac{1}{2\pi } \int_{- \Omega }^{\Omega } ...
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1answer
514 views

H-bridge output filtering

I'm driving A4952 motor driver with about 25khz PWM signal, with a simple coil connected as a load between OUT1 and OUT2. VBB is variable, testing with 15V but changing it doesn't alter the results. ...
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5answers
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What is the purpose of this simple 1 capacitor 2 resistor high pass filter?

I have seen the standard high pass filter with the -3dB cutoff frequency = \$ 1/2\pi RC\$. simulate this circuit – Schematic created using CircuitLab However I have seen this particular ...
0
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1answer
151 views

For a low pass filter, derivephase of the transfer function, Vout/Vin

simulate this circuit – Schematic created using CircuitLab I have calculated the magnitude: \$ ||H(j\omega)|| = \dfrac{1}{\sqrt{1 + {(RC\omega)}^2}} \$
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2answers
227 views

Simple LP filter - calculate cutoff frequency

If I am correct to calculate cutoff frequency in this LP filter I have to sum up the impedance of resistor and capacitor, right? simulate this circuit – Schematic created using CircuitLab ...