# Questions tagged [high-pass-filter]

A high-pass filter is an electronic filter that passes signals with a frequency higher than a certain cutoff frequency and attenuates signals with frequencies lower than the cutoff frequency.

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### How much power passes through the shunt component of a high-pass Pi or Tee filter?

I would like to send ~100W through an RF filter. Can you estimate the current passing through the shunt component without a circuit simulation assuming a reasonably high S21 value? MLCC's are cheap, ...
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### Chaotic Highpass Filter Output

I'm trying to build an RF transmitter circuit using LTSpice. Built a diode balanced signal mixer connected to a high pass filter to distinguish high frequency from low frequency. However, I'm kinda ...
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### concatenating first order high pass filters

I have the following circuit, which is an active high pass filter with the knee frequency $f_{-3dB} = \frac{1}{2\pi RC} = 1kHz$ I wanted to concatenate two of those systems in order to make a ...
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### Designing a second order HPF with a high gain common-source

I have a High gain (A = 22k) Common-Source circuit, and I was wondering If I can make a second order HPF like this circuit: My circuit is just an NMOS with an input at the gate, output at the Drain, ...
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### Second order active high pass filter

I am trying to design an active filter, which I assume is an active high pass filter according to what I see from the Bode plot. I can get the transfer function from this plot and then I need to ...
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### Noise of low-frequency RC high pass filter preamplifier circuit with LT1028

I want to build a low-noise and low-frequency preamplifier with the first-stage opamp of type LT1028 offering an input-referred voltage noise density of about $2~\mathrm{nV}/\sqrt{\mathrm{Hz}}$ at \\$...
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### Review butterworth high pass filter design

Could anyone review my 2nd order Butterworth HPF design? I have mentioned design details along with schematics and initial results. Design specifications for 2nd HPF: Cutoff frequency= 100Mhz, ...
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1 vote
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### Add Voltage Bias/Offset to 2nd-Order Sallen-Key Highpass

I need to add a highpass filter between a signal source and an ADC to get rid of high-amplitude low-frequency signals that would cause clipping. I built a second-order Sallen-Key filter and the ...
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### Why is the capacitor filter in parallel with the load and the choke in series in a choke input filter?

What will happen if we interchange them? In a capacitor filter, the capacitor discharges through the load, it was connected in parallel to load. From what I have concluded, if the capacitor is in ...
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### Need help choosing a toroid to wind an inductor for a high-pass filter

Trying to listen to HF but my RTL-SDR V3 is being overloaded by AM broadcasts so I'd like to build a high-pass filter to block the AM broadcast band. I thought I'd start simple and try making the one ...
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### What would the output waveform be in each of these cases?

In the second picture, the source is a step function from 0 to 1V. I feel like I solved them, but I am not convinced that my understanding is air-tight. Any help is appreciated. Edit: Adding my ...
1 vote
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### Removing noise generated by a servo from an audio signal

Background I'm working on an Arduino-based audio visualisation project where I run an audio signal into the Arduino, using an FFT to calculate the intensities at different frequencies and then using ...
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1 vote
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### Frequency response of a low-pass, band-pass, and high-pass adder circuit

I'm doing a project and one of the steps consists of filtering a signal through a low-pass, band-pass and high-pass filter. All the filters are Sallen-Key with a passband gain of 1. The pass-band ...
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### Why is the instrumentation amp distorting the signal on the input?

Here's my schematic. A current source is driving a resistive sensor. The sine wave is to mimic the behavior of the current real supply and doesn't play a role in the distortion. It's approximately ...
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### Active high pass filter experiment result

The pictures above are the circuit model and plot. uA741 of Texas Instrument was used as an op-amp on the circuit. 1 Vrms was used as an input voltage so that the output can be the voltage gain. The ...
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### Why do diplexer low-pass filter output have more inductors than capacitors and vice versa?

I am reading "Practical Radio Frequency Test & Measurement A Technician's Handbook" by Joseph J. Carr. On page 41, it has a diagram (figure 2.29 shown below). In that figure, why do ...
132 views

### Is using a passive RC high pass filter at the output of an opamp a good method to remove DC offset?

All the information I am able to find related to this discuss about AC coupling the inputs of an amplifier but never the output. I wish to know if there are any issues with AC coupling at the output. ...
81 views

### How does using a high-pass filter and an amplifier maximize the signal amplitude for analog-to-digital conversion?

I am currently reading the Fringe Contrast section of this document. This section says the following: Use a high-pass filter (HPF) and an amplifier (G) to maximize the signal amplitude for analog-to-...
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### How is this high pass filter?

I am new to electronics. I am watching this video. At 5:48, you can see the high pass filter: I understand the high pass filter, look at this: Then, I thought the first circuit should be like this: ...
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### How to remove the noise current values during CT disconnected?

i am doing a energy monitoring system. i have done High pass filter in the values of ADC current and getting correct. but when CT disconnected some current(noise) getting how to fix it. device - ...
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### How to calculate values for decoupling capacitors

For decoupling we just use a capacitor like 1 uF bulk and 0.1 uF ceramic caps at each power pin. But how are these values calculated? How many caps do we need to use in parallel? Can anyone explain it ...
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### Help understanding combined High/Low Pass filter circuit

I am a newbie and trying to understand the operation of this White Noise Coloration Filter - I have contacted the original author but at time of writing have bot received a response. The circuit is as ...
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1 vote
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### Trying to understand why op amp voltage follower goes high when fed negative input

I have a project where I want to take the positive and negative outputs of a passive differentiator and produce only positive pulses. E.g. when the switch feeding the differentiator is closed I get a ...
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### I need to design a second-order high-pass filter, gain 2 and cut frequency of 500 Hz. Using chebyshev response of 0.1 dB

I took the parameters from the MT-206 table of Analog Devices. I did not find in any book the chebyshev response of 0.1dB. https://www.analog.com/media/en/training-seminars/tutorials/MT-206.pdf I ...
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### How to prepare observation table and plot frequency response of Butterworth Sallen-Key High Pass Filter

My assignment: Design and simulate a Butterworth Sallen-Key High Pass Filter with the, fc = 10 kHz. Prepare the observation table and plot the frequency response. My answer so far: I want know how ...
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### Will capacitor in high pass filter pass high frequencies while it is blocking low frequencies?

I thought that capacitors will only act as a conductor while is is being charged and once fully charged it will not conduct any more. I know that current does not actually pass through the capacitor ...
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### How can I find the cutoff-frequency in real experiment?

My Problem is that I can't figure out how to answer this question: The component values in the previous measurements have been known and the cut-off frequency could be calculated. In real life, this ...
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### Is this a high-pass filter?

I am not very sure about how to completely solve this question. I tried to calculate the equivalent impedance by C and R and got R/(1+jwRC). Then I calculated the transmittance by using the voltage ...
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### Single capacitor for Powerline communication - AC coupling

First of all: I am not talking about traditional powerline communication (ethernet protocol etc) but about a very simple and primitive communication, like serial data transmission (https://en....
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We usually cascade filters in ascending Q-factor to avoid saturation in each individual stage. But are there advantageous situations when we cascade filters by descending Q-factor?
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### Use a Passive High Pass filter to filter out voltages from piezocrystal under a certain threshold

I have a piezo crystal (SEN-10293, datasheet: 7BB-20-6L0) that I am using to detect if a person sits on a chair. The compression of the crystal generates enough voltage to wake up a microcontroller ...
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### Output AC coupling: upper limit or lower limit?

I bought a DC2900A board for my project. In its datasheet it is stated: The maximum repetition rate of the pulsed laser should be 100kHz. The DC2900A repetition rate is limited by the output AC ...
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### Why is the output of a high-pass filter not 0 when the input is 0?

I'm trying to design a 5th order Butterworth high-pass filter built on the Sallen-key topology with a cut-off frequency at 100Hz. For some reason, the output has a DC offset of around 5mV when the ...
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### What is the behavior of electrons in a highpass filter circuit and what is an equivalent closed loop circuit?

I am being explained that an highpass filter in a circuit looks like this: It is hard for me to understand how this circuit works. Vin is AC voltage. I'm wondering what is an equivalent closed loop ...
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### Treble bleed frequency cutoff

I built an attenuator for my guitar amplifier. I took the circuit from here but left out the 4 ohm toggle since my amplifiers all have 8 ohm outputs. Below is a simplified schematic of the circuit (...
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### Transformation from Normalized Low-Pass Filter to Denormalized High-Pass Filter

I would like to ask a question about the a method (method number 2) to go from a normalized LPF to a HPF: Note: normalized refers to frequency normalization for the mentioned filters. 1- One method ...
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### Active highpass filter for microphone, how to choose cutoff frequency?

I am currently taking a class on filter design, and I am learning by doing. I want to make a small project by building a microphone circuit. I found online a tutorial by Great Scott. He made a circuit ...
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### Approximating the dirac delta function on LTspice to find the impulse response of a high pass filter

I have an assignment which requires me to find the impulse response of a high pass filter on LTspice. In order to do this the question suggest feeding a Dirac delta function as an input to a simple ...
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### Having trouble with an aviation-band receiver

I finished assembling an aviation band receiver that I bought online. I thought it would be good project for my resume, as I am an electrical engineer major at a University in California. I read the ...
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### How does this notch filter work? [duplicate]

I am trying to learn filters. In the following circuit, the author says that negative and positive feedback are used. I couldn't understand what the circuit parts do. Actually I got the negative ...
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### Variable band-pass filter for splitting audio signal into separate signals (high and low freqs)

I've been wondering for quite some time how to create a sort of audio splitter. The idea is to get an audio signal (e.g. guitar) at the input, and have two separate outputs, one with the input's low ...
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### Interpreting triangles in RC high pass filter circuit diagram

I came across the following image of a RC high-pass filter There is also an initial analysis that says that there is an initial condition for the output voltage that says $$v_O(0^-) = 0$$ which ...
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### Help finding multiple feedback (MFB) high-pass filter design formulas?

I can't seem to find some easily code-able formulas for MFB high pass filter. I have found plenty for the low pass filter, but absolutely none for the high pass filter. For example, the formulas on ...
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### Conundrum: High pass filter passes DC?

Consider a simple C-R 1-pole high pass filter. Apply a step input. The rising edge of the output rises up and then exponentially decays back to zero. Integrating the output over all times yields a ...
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### Transistor Amplifier Signal Drops Off Below 200-300Hz

I tried to build a dual transistor amplifier from a schematic I saw, and used AC Analysis in LT Spice. What I found was that the current and voltage at my simulated 8 ohm speaker load was dropping off ...
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### How to find a amplifier that named "ISP" on a circuit?

I am analyze the circuit. I can't find any relation about the name ISP of a op-amp. When we look the high pass filter we see there "ISP" name. I search it on google but I can't find nothing ...
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### best high pass filter topology to extract low V kHz range pulse from noisy 60Hz line voltage before daq

I need to extract a 1 kHz-10kHz range voltage pulse created by a current pulse I inject on an harmonic rich 60 Hz network and that propagates on it. The line voltage is 120V AC. harmonics 2 and 3 are ...
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### Detecting small AC current signal generated by phototransistor

I'm trying to detect a small AC signal (~10kHz) generated by a phototransistor on a magnitude of 10nA~1uA using the following circuit by converting the signal to voltage signal first and then filter ...
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