Questions tagged [filter]
A filter selectively processes input signals in frequency- or time-domain.
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My linear voltage regulator is overheating very fast
I'm using a 5 V / 2 A voltage regulator (L78S05) without a heatsink. I'm testing the circuit with a microcontroller (PIC18FXXXX), a few LEDs and a 1 mA piezzo buzzer. The input voltage is aprox. 24 ...
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How to know if this is a band-pass filter?
I have the circuit below. How can I see that it is a band-pass filter?
I tried calculating the equivalent impedance for the parallel part of the circuit:
$$\bar{Z}_{parallel} = \frac{\bar{Z}_C\bar{Z}...
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Transfer function of three cascaded RC filters?
I am looking for the transfer function of three cascaded RC filters:
I have found the solution for two RC cascades (components differently labeled):
$$H(s) = \frac{1}{s^2C_1R_1C_2R_2 + sC_1R_1 + ...
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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) = H_1(s)...
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3
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Why too many capacitors in parallel for Vdd supply net? Can't we just add all to replace with one big capacitor?
Here is a schematic of a Basys-2 board's power regulator IC and filters. It is just an example but this is fairly similar to many designs I've seen.
Why are there so many capacitors added in parallel ...
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Full-wave bridge rectifier with capacitor filter and ripple voltage
According to various sources, the ripple voltage of a full-wave bridge rectifier is
$$ V_r = \frac{V_s}{2}fCR $$
where \$V_s\$ is the peak of the input voltage source, \$f\$ is the frequency, \$C\$ ...
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How to calculate the gain of a RLC tank filter?
I'm supposed to create a passive bandpass filter to select a reasonably sinusoidal 750 Hz signal from a 250 Hz square wave.
Since we have very limited choices for the inductor (0.03 H) and capacitor ...
user186245
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2
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What does this schematic symbol marked SG1 looking like two arrows pointing to each other represent?
I know the symbol at the bottom is ground, but I can't get what the other symbol is. It can be a single symbol of two arrows pointing at each other, or two symbols each one a arrow.
I also have the ...
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TVS diode before or behind resistor
The best way to protect AVR pin for me is RC filter and TVS diode but I don't know one thing. I've seen schematics where TVS diode was before RC filter like in first schematics.
simulate this ...
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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_{\text{out}}\$ is measured right after \$R_1\$, which I suppose means that it is measured ...
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Why do reverse Bessel polynomials give rise to flat group delay in Bessel filters
I know that a Bessel filter has a maximal number of derivatives of the group delay at 0 equal to 0. I have never seen an account of what feature of reverse Bessel polynomials makes this so. Any ...
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Transfer function of Bessel filter
The Bessel filter transfer function is defined via Bessel polynomials. If we consider, for example, a second-order filter, the transfer function is:
$$ H(s) = \frac{3}{s^2+3s+3} $$
I wanted to build a ...
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Find the transfer function of this 3th order filter [closed]
I'm working on a project and I need to find the transfer function fhe following filter (as a function of the value of the capacitors and resistors). How can I find that?
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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 ...
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Gain in Sallen-Key filter
How can we increase the passband gain in a Sallen-Key type low pass / high pass filter, preferably without using additional op-amps.
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RC Lowpass Filter between Amplifier and ADC input
I have sensors (pyranometers that consist of thermopiles and measure sun irradiation) that ouput a low voltage signal so I need to amplify them using an instrumentation amplifier.
I have chosen the ...
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What is the practical reason for associating cut-off frequency to %50 power attenuation?
Historically when speaking about lets say an analog low-pass filter, the cut-off frequency of that filter is defined as -3dB.
So this is the frequency where the output sinusoid signal's amplitude ...
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Simple LM386 Circuit RC Branch Question
Please take a moment to checkout at the LM386 circuit below. The circuit comes directly from the LM386 specifications document:
My question revolves around the output branch consisting of the 0.05 ...
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Ignore Pulses Less than a Given Width in a Pulse Train
Let's say I have a 5V pulse train that varies between 0 and 75000 pulses per second. Pulse width, let's say, is 5 microseconds. How could I calculate or determine the best way to filter out all pulses ...
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USB 2.0 VBUS Filter
I am reading an old (2013) FTDI application note AN_146 about hardware design for USB 2.0. On the subject of VBUS filtering, it says this:
2.4.4 Ferrite bead use and placement – USB peripheral ...
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USB 2.0 HS: Common-mode chokes on DP/DM
The USB 2.0 specification seems to discourage the use of common-mode chokes on the D+/D- lines.
For example, in the USB 2.0 DC Resistance Engineering Change Notification (file ...
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3
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Confused with voltage doubler circuit
This is how the book explains the process:
Let me consider the first 90° of the input, the capacitor charges up to the peak voltage less the diode drop of D1, D1 is forward biased and D2 is reverse ...
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Input filter transfer function derivation
In the figure above, I am trying to design an input filter that attenuates all switching frequency harmonics from i_sys, such that i_batt is a DC current with vary small ripples.
My approach is to get ...
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Input filter to reduce conducted emissions caused by DC/DC converter
This material from ROHM explains the input filter design for a DC/DC converter.
The filter circuit is given below.
I understood the design of Lf, Cf2, Cd and Rd.
If you see the 3rd page (design of ...
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Strange noise on DDS
I have built an FPGA based DDS (fc=200MHz. out: 0-50 or 0-80 MHz) . I have a decent DAC output wave and now trying to build an appropriate filter for it ( Fig-1 ). The filter works rather fine but ...
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What is the best way to get a sine wave from a square wave?
I have square waves of different frequencies (1KHz to 20KHz), and I need to convert them to a sine wave of the corresponding fundamental frequency.
A RC ladder Low-pass filter was the first thing ...
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2
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How to find Vout for the following band pass filter
I have a problem finding the following Vout for this circuit.
Is it possible to just use the following formulas that i have shown. I am just unsure due to the resistors.
I assume that what i have ...
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What is impedance?
This is presented as both a resource for the community and a learning experience for myself. I have just enough knowledge of the subject to get myself into trouble, but I don't have the best grasp of ...
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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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Ripple voltage filtering capacitor
I'm an self-taught high schooler who's trying to understand how filtering capacitors work. I've searched and read multiple websites trying to understand how filtering works. At the point where I am, I'...
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How to compute input impedance?
I use a Sallen-Key filter for a project at university and I need to know its input impedance. Is there a way to compute it theoretically ?
Here is my circuit:
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Function of Specific Capacitor in Audio Amplifier's Negative Feedback
The audio amplifier that I am referring to here consists of three stages. Among others, the amplifier also includes negative feedback (NFB) that is made of two passive resistors.
From the base of TR3 ...
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Methods of filtering noise caused by DC brush motors
I am looking for any information that would help me reduce the power rail noise and EMI of DC brush motors. I am building a robot that is powered by 2 x 250 W 24V DC motors.
Thank you in advance
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Can you find the transfer function of two cascaded networks if you know their individual transfer functions?
If you have network N1 with transfer function H1 and network N2 with transfer function H2, is there a way to find the transfer function H3 for the network produced when cascading N1 and N2 (and ...
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Ripple reduction with LC filter
This seems like it must be a common problem but I don't find a clear answer anywhere, maybe my approach is wrong.
I have a DC-DC regulator in my circuit, which has a ripple of 50mV at 200kHz, the ...
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4
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Bypass capacitor vs low-pass filter
i'm trying to get my head round two intermingling factors relating primarily to an rc low pass filter and bypass capacitors for providing a low impedance path for high frequency AC signals, ...
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Using LC filter instead of RC filter in mains powered circuits
Above is a dimmer circuit. In some of these circuits I see a toroid inductor together with a capacitor forming a low pass LC filter which is called choke filter.
My questions are:
Why is RL used ...
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How to implement a discrete transfer function into an arduino?
I am here asking how does one transfer a difference equation into a MCU? I have never done it personally and looking into this topic I was never able to find a good answer. Its usually used with ...
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Is it useful to think of SMPS input capacitance as part of an LC filter?
I'm at the stage of learning about switched-mode power supplies that I'm focused on understanding the role of input capacitance. Just for background, I'm working with a buck topology for this ...
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3
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Physical significance of group delay
What is the physical significance of the group delay of a system/filter?. Why is the slope of the phase response critical in a communication system.
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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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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 negative-...
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Why use an opamp for the variable Q feedback in a Twin-T notch filter?
In the following circuit, for a Twin-T notch filter, the author is using an additional inverting op-amp for the T-filter "feedback", that is connected to a potentiometer (pot).
Image credit: here
...
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1
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Designing a Chebyshev filter: am I getting the order wrong?
I'm solving the following problem:
Consider the design of a Chebyshev lowpass filter with 3 dB DC gain, a passband limited to 1 kHz with a
maximum ripple of 3 dB, and a stopband characterized by AS = ...
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3
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What is the purpose of the three part circuit?
I'm studying for my final on introduction to circuits and came across a question about this circuit:
The question is:
Identify and describe the three parts of the circuit used for a measurement ...
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Detect ring signal using a low pass filter
I created 2 boards communicating each other like an intercom system. One of them has a button to send a ring signal to the other. The ring signal consists of PWM signals created by an MCU. I want to ...
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Roll-off of a filter
I know that the roll-off of a transfer function gain is given by:
$$20\log_{10}\left(\left|\text{H}\left(\omega_2\right)\right|\right)-20\log_{10}\left(\left|\text{H}\left(\omega_1\right)\right|\...
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Can I replace a PLL Charge Pump with an Active LPF?
Background
I am using a MAX9382 phase frequency detector in a project. The application notes recommend using a charge pump on the output of the IC. In PLL applications there is an up and down line ...
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High pass filter
Some one please help me with this question. I am getting -10.5 as the wrong final answer.I found the formula in the following slide.Since the result was coming out in complex number i got its modulus....
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If you were to add "DC offset" with a clamp, can you easily remove it afterwards?
I don't have a circuit right now, but let's say you wanted to add DC offset to a signal (ex. to prepare a signal for an Op amp stage) but then afterwards center that signal on 0v.
Is this possible ...
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