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

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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
43 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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117 views
+100

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
52 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
106 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 ...
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1answer
74 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\$, ...
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1answer
64 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
71 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 ...
2
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2answers
153 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
119 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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2answers
64 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
42 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
120 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
208 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
99 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
62 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
154 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
258 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
132 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 ...
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1answer
166 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
78 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
92 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
123 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
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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
149 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 ...
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1answer
81 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
154 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
108 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
701 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
129 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
56 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
378 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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996 views

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 ...
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1answer
140 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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185 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 ...
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1answer
71 views

Why is this LPF design passing frequencies above resonant in such magnitudes?

It's been a while since I have worked with filtering so I decided to simulate a circuit to see what I had forgotten. I used MultiSim for my circuit simulations but will present the design using the ...
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5answers
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Difference: Low Pass Filter and Large Capacitor?

When working with microcontrollers it is recommended to place filter/decoupling capacitors between a supply pin and ground. I understand the purpose of this implementation, namely that voltage across ...
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3answers
226 views

Question about RC charge-discharge curve

I found the following image on electronics-tutorials.ws: Isn't this wrong? Shouldn't the voltage rise faster during the first 2T than that it decreases during the next half period? I think so ...
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2answers
180 views

Dedicated digital filter

I have built a DDS (0-80MHz) with an FPGA (XC3S400) that I can program it for making almost any wave form (limited frequency by the wave form complexity). After weeks of struggling with making a ...
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3answers
366 views

Unexpected behavior of the Sallen-Key second order filter

I met an unexpected behavior when I simulated under Multisim (National Instruments) the Sallen-Key circuit given on the image below. The circuit is designed to receive a 1.8kHz modulated sin wave ...
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2answers
1k views

How to Calculate Complex Low Pass Passive RLC Filters?

I have designed a FPGA based DDS and now I want to add a low pass filter to its output. Previously I was working on a project based on AD9850 DDS(0-50MHz) and I had a commercial module for it that had ...
3
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2answers
2k views

What is the transfer function of n-cascaded RC filters?

Is there an explicit formulation for n-cascaded RC filters? The resistor and capacitor values are not necessarily same. Assume that: \$ R_i \neq R_j \$ and \$ C_i \neq C_j \$ for \$ i \neq j\$ and ...
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1answer
94 views

Why is there a lower limit on amplification for this filter design method?

I'm designing an active low-pass filter for a differential input. The input is on a ±100V scale and needs to be scaled down to the standard ±10V scale. I found this application note which describes ...
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2answers
157 views

how to set rc passive low-pass filter?

I have got a analog signal that include some unwanted ac noise. the noise amount is about 0.5 mv. I want to use passive rc low-pass filter but i don't understand which frequency that i need to pass. ...
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1answer
107 views

Confusion about filter transfer function

Today I got confused about Low pass filter transfer function. Let's assume we have a simple low pass RC filter . It is well known that at f=fc we expect -3dB (0.707) drop in Vin. Everyone knows a LPF ...
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170 views

Is this correct for non-inverting op-amp?

Do 0.1 uf and 100 k ohm act as low-pass filter in here?
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2answers
1k views

What are best values of a Low/High pass RC filter?

Cutoff frequency of a RC filer is obtained from well known equation: 1/(2 pi RC). This is one equation with 2 variables. for example R=100 , C=10 has the same result as R=10 , C=100. Which value is ...
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3answers
734 views

Why do RC circuit voltages decay *slowly* rather than instantly?

Let's take the simplest RC circuit imaginable: simulate this circuit – Schematic created using CircuitLab Now I think I properly understand why the voltage rises slowly after the leading ...
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2answers
243 views

Active low-pass butterworth filter design

I have a project on filtering out frequency above 2.5 KHz. The filter should be low pass butterworth. I am confused here as there are two cutoff frequencies I need to use. 1st cutoff freq. 1KHz and ...
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1answer
1k views

Arduino Motor Shield R3 Current sensing

I am trying to use current sensing functionality of Arduino Motor Shield R3, the shield is based on L289. The values that I read seem to be very noisy. I am using Arduino UNO A0 analogRead() function ...