A filter modifies signals based on their frequency.

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2answers
28 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
27 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
49 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 ...
3
votes
3answers
521 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 ...
0
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0answers
49 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
47 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
42 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
39 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
38 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, ...
52
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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 ...
11
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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 ...
0
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1answer
51 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
83 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 ...
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0answers
64 views

What's your electronics design question? Be specific [duplicate]

What are difference in this two circuits? We can find decoupling caps and a filter. Since filter should be of 88Khz and decoupling capacitors change it's value. It's correct to put filter after ...
2
votes
1answer
101 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
40 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 ...
4
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2answers
98 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). ...
0
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1answer
46 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
42 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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3answers
87 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
109 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. ...
0
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1answer
53 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
76 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
394 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
48 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 ...
0
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1answer
95 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 ...
7
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2answers
586 views

Use of 100K ohm resistor along with 0.1uF capacitor?

In the circuit diagram below, why is there a 100KΩ resistor (NOT R2) connected to the capacitor? To my understanding the capacitor-resistor act as a high pass filter to block the DC offset of ...
0
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1answer
58 views

Multi Stage Passive Filter Design [closed]

I'm playing around with some simple RF beacons, many of these use a multi stage LC ladder to filter the outgoing signal after passing through a class C amp. Can anyone point me to a good ...
1
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1answer
80 views

Frequency response of 2nd order RC low-pass filter

I am trying to calculate the frequency response of the following circuit: simulate this circuit – Schematic created using CircuitLab The two extra GND points are used to show that Vi and ...
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0answers
81 views

Calculating capacitor value for high frequency attenuation?

This question stems from the comments in this question regarding killing high frequency signals. In an active low pass filter, the -3dB frequency is given by $$ f_{3dB} = \frac{1}{2\pi R_2C} $$ ...
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3answers
65 views

Filtering the output of the “cheap MCU voltage inverter”

This is the circuit I have to create a negative rail for a local op-amp which needs the rail in order to manage to get low on the output rail. I've tried running a single supply but that did not ...
0
votes
1answer
96 views

RGB LED audio spectrum analyzer - Bandpass or FFT?

I'm about to build a coffee table which has a RGB LED matrix build in it just like in this video. https://www.youtube.com/watch?v=4NJDgvV8RZw I want the matrix to display an audio spectrum that ...
1
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1answer
123 views

First PSU - need help with capacitor size

I am building my first power supply unit (my first project too) and need help in figuring the size of filter capacitor (and type, though I presume Electrolytic) I need to use after the rectifier ...
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2answers
78 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 ...
0
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1answer
87 views

LC Low Pass Output Filters for Inverters

I need an output filter for UPS inverter. I am using 9.6kHz PWM and 60Hz frequency. Can anyone help me with the right filter as I am new with filter design?
1
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0answers
47 views

Why is it impossible to realize elliptic even-order filters with \$R_S = R_L \$?

Referring to RLC continuous-time prototypes of filters, I have read that an elliptic filter of even order can not have equal source and load termination resistances. The trasfer function for such ...
1
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1answer
61 views

Final voltage of two parallel (switched) capacitors

I am trying to obtain a resistance-circuit equivalent to a switched-capacitor circuit. It is the first stage of a ladder filter. simulate this circuit – Schematic created using CircuitLab ...
4
votes
1answer
137 views

Impedance matching with only capacitors?

I need to do impedance matching for 33 + j32 ohm source and 16.5 + j0 ohm load. The copper traces adds 99 ohm impedance and 20 degree electrical length. According to smith Chart below, I need to use ...
1
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1answer
166 views

Is this circuit block diagram correct?

I plan to build a flashlight powered by 360F 2.7V super capacitor (proposed to be charged to max 2.5V and discharged to min voltage of around 0.6V to increase capacitor life). The EMF generated by the ...
0
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0answers
35 views

3rd harmonic filter circuit to analyse leakage current

Anyone help me to design 3rd harmonic filter circuit using op-amp. Input voltage is 45V, 60Hz. The output should be in current 180Hz.
1
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2answers
45 views

Oscillating active filter

I built an 2nd order active highpass filter with cut-off frequency at 800Hz using an OPA847 (and R18=39.2k, R19=16.9k, R16=11.3k, R17=11.3k, C7=20nF, C8=20nF). Simulation works fine. In real life ...
0
votes
1answer
31 views

Sampling: how to determine a “good” sampling rate based on a given filter

I assume that the sampling rate is w_s = 2w_max if we have an ideal low-pass filter that nulls frequencies whose absolute value is higher than that of w_max. Therefore, that the only reason for ...
1
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2answers
55 views

Notch filter transfer function

For some active filter circuit I have derived the following transfer function: $$T(s) = \frac12\cdot{s^2+{1\over2R_1^2C_1^2}\over s^2+{1\over R_1C_1}s+{1\over2R_1^2C_1^2}}$$ I need to show that this ...
1
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2answers
269 views

Filtering DC offset of a pulse train

How can I filter a DC offset of a pulse train with an RC circuit? The signal is a pulse jumping between 3.07V and 3.53V. But I need a pulse which is jumping between 0V to 0.5V. How can I filter that ...
1
vote
4answers
84 views

Using Differential Amplifier to reduce required RC values

I need to implement a low pass filter to convert a 20kHz square wave into a 20kHz sine wave. It would be nice to be able to use lower values, because in CMOS large resistors and capacitors take up ...
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votes
1answer
52 views

AC Analysis Mindset [closed]

I'm just trying to solidify my foundational knowledge of ac analysis. So when approached with a basic circuit, lets say a RLC circuit, should my first instinct be to convert each group of components ...
0
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1answer
122 views

RC Filter Circuit Question

Given the image below, we know that the second filter circuit is a Passive Low Pass Filter circuit. I'm assuming it is still a Passive Low Pass Filter with a different corner frequency. Am I correct? ...
0
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0answers
34 views

Time response of a RC polyphase filter

I'm simulating a circuit using cadence for my master thesis. I'd like to use a RC polyphase filter to get in output a square wave using when the input is a square wave - basically the two wave should ...
0
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0answers
27 views

Suppressing interference in a pressure sensor circuit

I just looked over a circuit designed by my predecessor, which is used to interface with a pressure sensor. It works, but I have some doubts about the way the input filtering is done. The simplified ...
1
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2answers
147 views

what frequencies do caps filter?

I've been trying to find out what frequencies get filtered out by which type and capacity capacitors, but cannot find simple rules that say "type X, cap Y filters xxx (k/M)Hz - yyy (k/M)Hz". Yet ...