# 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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108 views

### 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 ...
50 views

### 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 ...
42 views

### 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 ...
793 views

### 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 ...
56 views

### 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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### LPF 12dB/octave design

I'm designing a diode limiter for audio use where the signal is high passed through a discrete transistor circuit. After the diode stage the signal would need its low end restored and I'm struggling ...
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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 ...
426 views

### 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 ...
49 views

### 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 ...
904 views

### 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 ...
81 views

### 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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I'm studying filters. In particular, I'm studying low-pass to high-pass filter transformation. I know that you only need to design an equivalent normalized low-pass filter and then, by using a ...
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### How to apply high gain to filtered signal without shifting voltage level?

I have an op amp gain circuit at the output of a 2 stage filter. It seems like at high gain settings (x500), the steady state voltage shifts significantly. I am trying to keep it at ~1.7V and it ...
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### TPA0253: Help Understanding Mono Output

I'm working on implementing an audio amplifier into a circuit design, and I am trying to understand the output configuration for the speaker using the TPA0253. I will be using a 8 ohm, 1W speaker for ...
174 views

### Band-pass filter vs. Serial Low-pass+High-pass filter - Is there a difference?

Is there a difference between a band-pass filter (BPF) and tying a low-pass filter's (LPF) output to the input of a high-pass filter (HPF)? It seems to me that they should do the same thing---or ...
36 views

### High pass filter that locks voltage at certain amount until frequency is reached

I have a sine wave that is biased at about 1.5V DC. I want to create a high pass filter that allows any frequency through greater than 4000Hz. Want I want my high pass filter to do is to be at 1.5V ...
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### What change should I make in my Lead Compensator circuit below to reduce the DC response? Vin be sine wave with variable frequency

I want to increase my cutoff frequency, Fc. As Fc=1/2piR*C, Should I reduce the value of either resistor or capacitor to increase my cutoff frequency?
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### Why does this high pass filter behaves like band-pass filter on Multisim AC Sweep simulations?

I have this high-pass filter schematic and its AC Sweep simulation. Until the break through the end, the graph is right but I can't see why the graph breaks on the right hand side and filter behaves ...
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### Shared via on 22pF cap only used to smooth differential clock signal?

Google's so cluttered these days, it's hard to find simple answers. I've got differential clocks running around 500MHz (1000Ms). There's some optional 22pf caps on each Address line, going to the ...
108 views

### Finding transfer function and tuning cutoff frequency of High-Pass FIlter

I have a schematic for a High-Pass filter that has a cut-off of around 7Hz. I obtained the designed online and want to tune it to have a cutoff of 5Hz instead. I assumed I would proceed in the ...
365 views

### High pass filter - Cut-off frequency calculation doesn't match simulation

I have made the following simulation with the circuit you can see below: I'm asked to find the cut-off frequency for this filter. From the simulation, it looks like it $f_c = 500 \text{Hz}$ or ...
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### Dielectric absorption in capacitor (audio crossover)

I want to understand the selection of a proper capacitor type for a simple audio crossover (passive lowpass filter before woofer, passive highpass filter before the tweeter). Various blogs more or ...
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### Analysis of a high-pass filter

I'm doing some analysis of op-amp circuitry including the high-pass filter shown below. I was given three questions to try further my understanding on the analysis of such system. However, I am ...
84 views

### How to derive the gain (ratio of output voltage to input voltage)

$$\frac{V_c}{V_s} = \frac{\frac{j}{\omega\cdot C}}{R+\frac{j}{\omega \cdot C}}$$ Given this starting formula, how to rationalize the denominator and find the gain?
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### How is dc restorer circuit used for PWM demodulation/detection?

In the Microelectronics Circuits textbook by Sedra & Smith, it is said that: As an application, consider a pulse signal being transmitted through a capacitively coupled or ac-coupled system. ...
134 views

### How to calculate cutoff frequency for a high pass filter in DC biasing circuit

I would like to DC bias an AC signal using a voltage divider as shown in the following schematic. I realise the bias point would be subject to noise from the power rails, but that is not a concern for ...
199 views

### how to design a low pass filter for square waveform

I have square wave signal of 100KHz with few high frequency ringing from 555 timer.when i tried to use a 100KHz first order rc low pass filter,i got a sawtooth waveform because the 100KHz square will ...
1k views

### How to remove DC offset (and make average DC value 0V) from ADS1261 square wave AC-excitation circuit

I am attempting to remove the DC offset from the 1 kHz, ± 2.5 V, AC square wave output pins of an ADS1261 (http://www.ti.com/lit/ds/symlink/ads1261.pdf). However, when measured on the oscilloscope (...
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### PMOS unexpectedly passing current with capacitor on drain

I am designing a circuit to get a pulse when a switch opens. When the voltage source V1 is connected, the switch SW1 starts closed. I want Vout to briefly go high when SW1 opens. The circuit I ...
805 views

### Low pass filter not working properly

This is the pass band that I'm using to filter some EMG signals through electrodes. When I test it with multisim it works really well as you can see, but when I test it with real equipment (...
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### Synthesizing this simple analog notch filter?

I want to synthesize this simple analog audio filter which is a notch: The inductor with resistor creates a simple one-pole low pass filter with the cutoff frequency at: fc = 1/(2pi L R) The ...
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### Audio HPF cutoff frequency selection

I need to use a HPF for my headphone amp and I want some suggestions about at what frequency I should place the cutoff frequency. Currently I want to use a HPF with a fc=15~20Hz but this gives me -...
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### What condition must be verified by the frequency so that an RC circuit acts as a differentiator? [closed]

So I am theoretically planning to make an RC differentiator circuit but I'm still a rookie with it so if someone can help me it would be appreciated.
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### Should Passive LPF/HPF Component Selection Depend on Ability of Input to Source Current?

When choosing R and C for a passive LPF or HPF, should you take into account the input's ability to source current? I'm currently working on a passive HPF for an input that can supply up to 10 mA @ 3....
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### $V_o/V_s$ of given circuit

I'm trying to calculate $$\frac{V_o}{V_s}$$ of the given circuit, but don't really know what to do with the voltage dependent voltage source. As I'm not an engineering student, this stuff is very ...
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### Need help in designing a BJT Amplifier with Avnl = 100

For our final project, we need to design a "single-stage BJT-based highpass amplifier using voltage divider configuration". The amplifier has the following requirements: \\$V_{CC} = 12V, f_L =...
109 views

### RC filter for emitter follower input

Please could someone explain how to compute the impedance with which to determine the frequency characteristics of the high-pass input filter in the following circuit? My question is prompted by an ...