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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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Why is the cutoff frequency of this highpass filter with formula different from LTspice?

I used this online tool to play around and design a Sallen-Key low pass filter with a cutoff frequency of 0.3Hz. When I now put the resulting values for R1, R2, C1 and C2 in the formula I get exactly ...
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High pass shunt filter

I have a DC motor, which is used as an electromagnetic brake. However I want to leave certain frequencies uninhibited, so I thought this should be possible by adding a shunt filter on the DC motor ...
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147 views

High pass filter for use in amplifier circuit

I've designed an amplifier for a small ac signal (amplitude of around 5mV, frequency 252kHz) with a BJT (2N2222.) The BJT is set up in a common emitter amplifier configuration, with the biasing ...
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49 views

Is the Roll-Off of Butterworth Filter of degree N always N*20db/dec?

I am trying to implement a fourth order Butterworth high pass filter under a Sallen-Key topology. Two frequencies, one at the passband and another for the stopband, are set to be at some specific gain/...
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98 views

Are my calculations wrong for the capacitance?

In an earlier post i discussed about the effects of voltage derating on a capacitor. From here i measured the output with DC and AC applied to a highpass filter and found the cutoff frequency with the ...
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103 views

How to generate this kind of filter?

I've been trying to understand this exercise proposed by my teacher. He asked us to find a combination of 2 ideal filters to generate a filter within the conditions of the image below. (That means, ...
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65 views

Amplifier and Low Pass filter not responding after few minutes of correct output?

I am trying to design an amplifier and low pass filter circuit for a piezo sensor. My frequency of interest is .3 Hz to 5 Hz, for first stage I have used charge amplifier and the subsequent 3 stages ...
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164 views

High pass filter for electret mic to mobile phone

I’m currently working on making a lavalier microphone for use with my phone and gopro camera. I know these types of microphones are readily available and can be purchased fairly cheap, but where would ...
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309 views

Differential Equation of a First Order High Pass Filter

I am just stumped right now b/c I do not know how to write the "differential equation that describes this system. I did learn to write equations with impedances but I believe this is not what this ...
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121 views

X5R capacitor derating and highpass filters

X5R capacitors derate to about roughly 85% when DC voltage is applied, from what I have been told. Does this have an effect on high pass filters, even though HF filters off DC (0Hz)? If I wanted to ...
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156 views

Using capacitors for ethernet isolation? [duplicate]

The standard for ethernet says you should use a transformer for isolation. It seems like a cap-based solution would be smaller, more versatile, and a better fit for my application. Is there any ...
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77 views

How can one of the RC networks of this active high pass filter topology work as an actual high pass filter?

I have seen some previous vague questions related to a similar case but not for this topology. The following circuit (source: http://stompville.co.uk/?p=470) shows an alternative topology for an ...
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368 views

How to calculate the transfer function?

I have The following circuit network (link to multisim) and i am asked to find the transfer function, the max and min value, the cutoff frequency, angle and the type of the filter. [the actual ...
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58 views

Designing a Band Pass Filter

I need a band pass filter that only accepts frequencies from 1000 to 1400 Hz and then toggles the transistor. It has to work from .1 Vpp to 1 Vpp and rejects anything else. I have been testing this ...
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273 views

Bode Phase Plot of RC High-Pass Filter

I have been trying to understand Bode Phase Plot of RC High pass filter. I know that from my engineering that voltage lags behind the current passing through the ...
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342 views

High Pass Filter Design from Transfer Function

I need to design a circuit that implements the following transfer function: \$G(s)= G\frac{s+z}{s+p}\$ where, G = gain, p = pole and z = zero.
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158 views

change level of positive square wave signal to negative

A general question: Lets say I have a square wave signal from 0 to 5 volts. What I would like to do is create a circuit that will convert this 0 to 5-volt signal to a -2.5V to +2.5V for example. ( ...
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64 views

What's this amplifier filter configuration?

I've come across an audio amplifier circuit that contains this following configuration: I recognize R1,C1, and R3 to be part of a first order high pass filter, but I'm not sure what C2 and R2 are for....
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712 views

High Pass vs Low Pass simple Circuit (RC vs CR)

In an RC circuit, where the resistor comes before the capacitor, the circuit acts like a low pass filter. Whereas in a CR (I don't know if that is how you say it) circuit, where the capacitor comes ...
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How ac coupling in scopes does not give you a phase shift? Or does it?

For what i know, filtering something always gives some amount of phase shift. So how do oscilloscopes with ac coupling don't have that? Do they correct in software? If so, how they used to do it at ...
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91 views

Negative Voltage Shift from Blocking Cap for Amplifier

Recently I have been working with the Analog Devices AD797 op-amp in LTspice, and have been getting poor performance from the amplifier when using a low-amplitude signal. This is my circuit in LTspice:...
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81 views

By replacing capacitor values with different ones in a circuit, will the circuit still work? [closed]

I'm fairly new to electronics and following this schematic for a "Truth Meter", which detects sweat from your fingertips and a lights up an LED depending on the resistance of the skin, as one of my ...
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Physical significance of positive group delay with negative phase delay

This question is an addendum to: Is group delay the same as the delay of a certain frequency? Lately, I've been going back to basics to better understand the concepts of group and phase delay, so I ...
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46 views

Transmittance of a capacitively coupled shunt resonator

I have been trying to understand the expression of |s21| for the resonator mentioned in this article. For a circuit similar to the drawn below, in which R1 is used as the temperature sensitive element,...
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167 views

How to calculate cut-off frequency for T section high pass filter?

This is a high pass T filter: According to me, if input voltage is \$V_{\text{in}}\$, then voltage across the inductor \$L\$ should be $$V_x=\frac{j\omega L}{j\omega L + \frac{1}{2j\omega C}}V_{\...
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RL filter output attenuation

I am designing high pass RL filter. R is 550 [Ohm], L is 220 [uH]. I calculated that time constant is therefore 0.0000004 [s] and -3 dB pulsation 2 500 000 and frequency 397 887 [Hz]. I put this on ...
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74 views

Understanding Working of High-Pass RC Filter

I was trying to visualize what happens when frequency is swept from 1Hz to 1GHz. In case of capacitor, voltage lags behind current by 90 degree and capacitor reactance depends upon it's frequency. I ...
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1answer
94 views

The Art of Electronics 1.35

Forgive me if this is not the proper question format. Please critique it if not. I am new to this site. I am reading "The Art of Electronics" and cannot understand the jump made in equation 1.35 to ...
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57 views

High pass RL circuit angular frequency

I am answering this question as shown in the image. I had no trouble deriving \$\frac{V_{out}}{V_{in}}\$ in the first question(answer is \$\frac{j\omega L}{R + j\omega L}\$ I also had no trouble ...
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148 views

High power tolerant (10-20 W) LC filter

I need to build a passive high-pass filter that has a cutoff frequency of 2-3 kHz. Sounds simple? It needs to pass between 10 and 20 W rms power at 20 kHz without overheating and going "bang". ...
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1answer
50 views

High power highpass filter

I'm using an audio amplifier to produce a 15-20 kHz, 6 watt sine wave output into a pure resistive load. There are some low-frequency components to this signal that I want to remove (mains frequency ...
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47 views

Type of filter to use for charges consumption

I am trying to study correlation between many time series of electricity consumption ( in voltage in time ). I have several problems, the data isn't continuous, I only have observation each 15 min, ...
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198 views

Change in gain and cutoff frequency of 2nd order passive filters due to amplifier circuit

I'm designing an simple equalizer for a first course in Electric Circuits and having some problems. Circuit diagram and AC Sweep Simulation (Multisim 14): Circuit Diagram AC Sweep Simulation The ...
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159 views

A weird question about the cutoff point of an RC low pass filter

I have read the linked explanation about the RC low pass filter circuit and understood most of it. I understand the relation between the time constant RC to 1/(2*pi*f_c). I understand it means there ...
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148 views

Use of resistance and capacitor in filter

In the band pass circuit what is the role of resistance and capacitors? How do there arrangements don't allow some specific frequencies? band pass filter circuit
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298 views

RC Filter Parallel Potentiometer

I am trying to teach myself electronics, namely audio filtering, and I came across this circuit. Now with my limited knowledge the 'volume potentiometer' (that's what it is explained as) seems to be ...
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259 views

How to block DC of triangle waveform from 555 powered by single supply?

I'm using a 555 timer to generate a triangle waveform with a DC offset. I would like to feed the waveform into a comparator along with an AC signal with zero offset to get a PWM signal, so I need the ...
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Second order High pass Butterworth Filter design

I am studying the designs of Second Order Butterworth high pass filter practically. The Capacitor values C1 and C2 described in standard textbooks are always in the range of picofarads.(e.g.,0.0047uF)...
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Why the DC voltage doesn't affect the high pass with the NMOS Transistor?

By changing the gate-source voltage of the NMOS transistor, I can alter the resistance in the triode region. The transistor becomes a voltage-controlled resistor. I don't understand how it affects ...
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Why the current in the drain of NMOS transistor is going to negative?

I am new at studying microelectronics and I really want to understand why the current in the drain goes to negative (you can see the plots in the attached files). When I am decreasing the voltage to 0....
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Why we use a 2nd order filter to build a higher order filter?

Why would we use 2nd order filters to build a higher order filter, like a Sallen & Key and others? Is the oscillation problem in higher order filters?
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197 views

Problems with designing a bass booster

For my university project I'm trying to flatten out my bass frequencies while keeping the other frequencies intact. (The idea is to first amplify a part of the input signal and input this signal into ...
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82 views

Trying to find the signal in an AC line

I have a medical office call box/light system that is older probably 20 year old and they moved the main panel that the Drs see to know when there are patients waiting and since they moved it, it is ...
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When talking about input and output impedances, what are we comparing them to?

Let's consider a theoretical highpass filter: simulate this circuit – Schematic created using CircuitLab I'm trying to show that the worst-case input and output impedance is R but the whole ...
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2answers
2k views

How to design a 2nd Order High Pass Butterworth filter with a gain of 6 dB?

I have been trying to design a 2nd order filter with a gain of 6 dB (or 2 Av), using the following Sallen-Key Topology. I have calculated R1 and R2 to give me a desired cut-off of 1.6kHz and this ...
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137 views

One-wire concept for WS2812B - adding signal onto DC

I would like to reduce the amount of lines for a string of WS2812B RGB LEDs for a project. In my understanding two lines should be sufficient, since we can modulate the signal onto the DC line. ...
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175 views

How do High and Low Pass Filters function [closed]

I dont understand how Low Pass Filters function .Like when the Frequency is very small the capacitor behaves Like an Open circuit . And when the Frequency is very big the capacitor behaves Like a ...
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113 views

How does this high pass filter in a mini color organ function?

I am trying to figure out how this filter circuit works: The filter is part of a mini color organ from Forrest Mims Engineer's Mini-handbook. I know it is a high pass active filter which will only ...
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1answer
193 views

Why does my cutoff frequency not match the 3db down point?

My understanding is that the cutoff frequency of this circuit can be calculated simply by: 1/(2*pirc) I get a cutoff frequency of 15.9kHz But as is shown in the provided bode plot 15.9kHz is ...
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1answer
86 views

Filter for Spectrum Analyzer

I want to build a data acquisition device to collect electromagnetic interference signatures of household appliances on the home electrical network (power line). In fact I hope to harvest datasets ...