A filter modifies signals based on their frequency.

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Confused about virtual ground circuit

I have a low pass filter in spice made of several stages but they look similar to this except I have a small resistor to gnd at the positive terminal: The design was done using a positive and ...
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0answers
42 views

Low pass filter

How to determine low pass filter output magnitude? For example I have input signal \$0.8\cos(2\pi 10t+45^{\circ})\$, and measure a voltage of the form \$A\cos(2\pi ft+\phi)\$ at the output. How to ...
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2answers
253 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 ...
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2answers
58 views

Looking for a simple way to inject a signal on 60Hz Mains line

Okay, so I'd like to be able to inject a really simple signal on top of the 60Hz AC Mains. It doesn't have to contain any data per se, just a simple signal to trigger a receiver on the same ...
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2answers
27 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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1answer
143 views

Why such unusual RC filter?

I have a test board with 2 audio chips: WM8533 and AK4954A. Their outputs are connected to headphone plugs like that: ...
2
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3answers
70 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 ...
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1answer
21 views

Why is a Buffer+RC-combination recommended for driving a SAR ADC analog input?

In various places, e.g. this tutorial video by ti, a circuit like the following is being recommended to drive the analog input of a SAR A/D converter: simulate this circuit – Schematic ...
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1answer
17 views

High Selectivity of Filter

For obtaining high selectivity, all natural modes should be complex conjugates (except for odd ordered filters). Why this condition? Thanks.
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1answer
53 views

Filter noise from a high voltage DC-DC converter

After finding a couple of triodes lying around I decided to build a valve preamp. I've built a simple boost converter based on a 555 timer to generate anode voltage. The circuit is powered from a ...
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2answers
61 views

Does adding a capacitor with a transformer makes it a LC filter?

when i add a capacitor with a transformer is a LC filter formed? Moreover if it acts as a LC filter then what inductance to be considered for checking the frequency response of this filter, whether i ...
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35 views

Low-pass RC-Filter with load problem

this is my first time posting here so my apologies in advance for any missteps. I have a homework problem where I am trying to find the Gain of the system. The circuit is similar to this one: ...
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1answer
37 views

Where to get PSPICE models of ceramic resonators?

I wish to design and simulate IF filters using ceramic resonators and crystal oscillators in OrCAD Capture or LT SPICE. The default libraries don't have any ceramics, so anyone know where to download ...
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28 views

determining appropriate group delay for FIR filter in matlab

I am trying to take a signal where the frequency with the max energy is about 180Hz and use a filter to distort that frequency by using a group delay. So far I have had no luck with matlab commands,I ...
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1answer
42 views

Finding component values of bandpass filter with load?

I have to find the components of a bandpass filter given only the two corner frequencies. The only components are \$C_1\$ and \$R_1\$ for the high pass, and \$R_2\$, \$C_2\$, and Load resistance ...
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0answers
46 views

Band-pass filter time step too small error in Proteus

I'm trying band pass filter circuit and having this error . here is the circuit diagram & the schematic file Sallen key. U3(+IN) & U3(-IN) = 50mv sinusoidal with some phase difference. ...
2
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1answer
34 views

Buffer between high pass and low pass filter when making a bandpass filter?

For a passive filter stage, I want to combine a high pass filter with a low pass filter to create a bandbass filter. Can I just make a simple RC circuit for each and connect them together? Or would we ...
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1answer
59 views

Should I use a passive or an active filter?

simulate this circuit – Schematic created using CircuitLab I need to design an am receiver as a project. On the front end I have three modules; BPF1 the "roofing filter" or the ...
2
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1answer
41 views

The advantages and disadvantages of the monolithic filters

Recently I noticed there are some monolithic filters on the market, such as http://www.linear.com/product/LTC1065. I want to know what's their advantages and disadvantages comparing to the normal ...
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1answer
71 views

Band pass filter unstable and lower gain than simulation

I’m trying to make an ultrasonic distance sensor and got the 40kHz emitter working but am struggling with getting the receiver circuit working properly. At first I just amplified the output of the ...
3
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3answers
358 views

Why is series LC circuit not behaving as band pass filter?

I am trying to simulate LC circuit using external source that generates square wave of 503Hz of amplitude 2V as below: Natural frequency of circuit above is 503Hz.So it must pass this much ...
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1answer
90 views

Unexpected dominant pole in active-RC circuit

Consider this active-RC circuit: simulate this circuit – Schematic created using CircuitLab it should exactly realize the RLC high-pass filter with one zero: simulate this circuit ...
3
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2answers
239 views

Deriving 2nd order passive low pass filter cutoff frequency

I'm working on a 2nd order passive low pass filter, consisting of two passive low pass filters chained together. simulate this circuit – Schematic created using CircuitLab Let \$ H(s) = ...
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4answers
397 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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0answers
42 views

Reducing noise for a TDA8947J amplifier

I have an PC audio amplifier using TDA8947. One 30W subwoofer and two satellites. It produces a lot of background noise and I would like to cut it down a bit. The noise is all in the subwoofer. It ...
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2answers
33 views

ATmega32 withRC filter and OpAmp

In my circuit (picture below), ATMEGA32 output is connected to a RC filter (R=100K, C=10uF 63V) to non-inverting terminal of OpAmp (LT1006). OpAmp is configured as voltage follower (Buffer Amplifier). ...
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0answers
46 views

From RLC prototype to signal flow graph

This simple 3rd order low-pass circuit simulate this circuit – Schematic created using CircuitLab can be described with the following 3 equations: $$-V_1 = \displaystyle \frac{-1}{sC_1} ...
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1answer
55 views

Don't understand high pass filters?

Consider a RC circuit functioning as a high pass filter. The transfer function is given by: \$T(j\omega)=\frac{K}{1-j(RC/\omega)}\$ For a frequency of 0, the transfer function is 0. Which means for ...
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3answers
554 views

Why does equal resistance and capacitive reactance lead to 70,7% of the output signal?

I think I'm somewhere half way through to understand it. Considering an ordinary voltage divider like this: the output voltage is independent of the frequency and is equal to the ratio of these ...
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0answers
62 views

How does this single-ended to balanced circuit work?

This comes from the sparkfun jamboree bluetooth audio board schematics (https://cdn.sparkfun.com/datasheets/Wireless/Bluetooth/Purpletooth_Jamboree1.pdf) How exactly does this work? With S7 in ...
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1answer
51 views

Multimeter reports voltage but no power?

I have an Insteon FilterLinc, which is an electrical line filter. It doesn't work. When I connect a lamp to the "filtered" outlet, I get no power. So I stuck multimeter probes into the filtered outlet ...
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0answers
43 views

Frequency detection and relay activation

I need a circuit (preferably not using microcontrollers for ease of assembly) to detect a frequency drop in the supply of an electric motor (speed drop) and activate a relay. How can I do this? ...
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0answers
42 views

Noisy analog output

Analog output filter design like below sometimes send 1 volt voltage spikes when driving servo motor, what may be the reason for that, any problem with the filter design ?
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1answer
54 views

How do I pick an inductor(s?) for an LC filter on a power rail?

I'm using a TI SN6501 transformer driver to provide an isolated power supply for a project I'm working on. However, it is imperative that the output power rail be as clean and noiseless as possible, ...
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14answers
5k views

My understanding of RC circuits is broken

I asked a relatively simple question. Unfortunately, the answers provoke far more questions! :-( It seems that I don't actually understand RC circuits at all. In particular, why there's an R in ...
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2answers
2k views

Is a capacitor a high-pass filter or a band-pass filter?

This has been bugging me for a while now... Does a single capacitor, on its own, behave as a high-pass filter or a band-pass filter? In a crystal radio set, you use a single capacitor as the tuning ...
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2answers
76 views

What does the output waveform from audio source look like?

I understand that every audio waveform will be different but in terms of frequency and amplitude what can I expect? The audio source is an audio jack connected to an Ipod or computer audio jack. What ...
0
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3answers
84 views

Circuit Starving Question

I have a circuit where 2 DC motors are connected to 4 AA batteries and being controlled by an Arduino microcontroller. Whenever the motors start, they starve other components in the circuit and it is ...
2
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1answer
107 views

Correctly choose circuit decouplers and filters and schematics advice

I want to ask some help to correctly design a power supply circuitry with TPS799 voltage regulators. I've this reference circuitry: And nothing more explainations. I want to use same specifics of ...
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2answers
50 views

Question about the derivation of RC Filters frequency cutoff

We've learned that the operation in RC filters depends on how the capacitor reacts to different frequencies, in other words, the capacitative reactance. The input is applied in series with a ...
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2answers
102 views

Optocouplers for purposes other than galvanic isolation?

In the diagram below there are two modules, A and B, which are separated by a physical distance of about 15m. Module A has a 12V DC power input. Module A powers module B (they share a common ground). ...
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1answer
58 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
65 views

Common mode RC filter of High-BW differential line

I'm using a fully differential analogue chain, using 20Hz HP, 3MHz LP and x2 Gain. My signal of interest is fully differential with a 200KHz fast modulation and a 100Hz sawtooth ramp. The high ...
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4answers
145 views

How to easily calculate transfer function of an LC filter

Consider a simple LC network: simulate this circuit – Schematic created using CircuitLab Is there an easy way to compute its transfer function in the Laplace domain? I would consider as ...
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3answers
125 views

Are there good free software analog filter design tools? If not, why?

I'm finding myself needing to do a fair bit of analog filter design. Mostly passive LC ladder filters. I honestly don't know much about how to design them by hand, I've been using the Genesys tool. ...
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1answer
67 views

filters for in-amp, difference amplifier, and non-inverting op amp

I am new to this matter and would like to learn how could I determine the right filters to use for my circuit. I have read some tutorials about active and passive filters but can't get the right ...
0
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1answer
88 views

Circuitry filters and decoupling capacitors example

I have some question that i want to ask using an circuit example. What help provide an inductor in Vin and Vout, a short of noise filter? Can i change voltage regulator and maintain same inductors ...
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5answers
485 views

Why does a sallen-key low pass filter not work with virtual ground?

I've been reading an article discussing single-supply op-amp design. Regarding Sallen-Key low-pass filter circuits, the author states that: A few filter topologies, such as the Sallen-Key low ...
0
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1answer
68 views

Filtering Noise on Strain Gauge Circuit

I am making a digital weighing scale circuit and currently having difficulties understanding filters that are commonly used to reduce noise in these type of circuits. My load cell is a full-bridge ...
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1answer
97 views

For what use is this circuit?

I need to power up an IC, but there is no description of reference design. Just an image. This is the image: This is a circuit to add to IC. But i can't understand it's use. Do it provide me a ...