Questions tagged [cutoff-frequency]

A cutoff frequency is a frequency boundary in a system's frequency response at which the power level is greater or less than a given fixed value.

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39 views

Second Order Butterworth LPF Cut-off frequency determining from graph

I am trying to design a butterworth low pass filter with corner frequency at 2khz as seen below. And my problem is when I find its transfer function It is as follows: \$H(s)=\dfrac{1}{1+1.414\times (\...
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41 views

Bandwidth of low pass filter: measured with the cut-off frequency?

I have the following Sallen & Key lowpass filter: $$T(s)=\frac{\frac{1}{R_1R_2C_1C_2}}{s^2+(\frac{1}{C_1R_1}+\frac{1}{C_1R_2})s+\frac{1}{R_1R_2C_1C_2}}$$ The parameters values are \$R_1=10 k\...
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38 views

Setting the cutoff frequency of an active bandpass filter (op amp) and finding the phase in LTSpice

I am doing an exercise and my op amp cutoff frequencies are: lower 1kHz, upper 10kHz. I have found the phase shift of the filter, but since the graph I get does not make much sense for me I think it ...
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1answer
107 views

Cut-off frequency of a LED

I'm trying to solve this problem: A GaAs LED is at \$ 300 K \$ when the current density is 1000 \$A/cm^2\$ . The width of the active region is \$ 1 µm \$. Assume that, for that current, we are in the ...
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89 views

Sallen-Key Low Pass filter

I was trying to do a project on LT spice for the frequency response for Sallen-Key low Pass filter. But when I tried the Following circuit, I am getting a roll off 20db / decade instead of 40db/decade....
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1answer
57 views

Finding upper cutoff and lower cutoff frequencies on notch circuit

I need to find upper cutoff (UCF) and lower cutoff (LCF) frequencies based on formulas of a notch circuit, but I'm getting a quadratic equation (as expected) with an imaginary number (IN; not expected....
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Can I change a frequency band of an EQ board?

Is it possible to change one of the frequency bands of this EQ board? In particular, the low frequency adjuster is 100Hz and I want to make it 60ish Hz. My understanding is that i need to meddle with ...
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38 views

Cutoff frequency of stacked low pass RC filters

How can I determine the cutoff frequency of a filter between V1 and the output marked with the red arrow? All resistors and capacitors have the same value. In the picture is a stack of battery cells (...
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3answers
239 views

What is the formula for cutoff frequency for LCL filter?

I have an assignment for school and one of the questions is asking me to find the "bandwidth" of a "pi filter." This teacher miss words things sometimes and I know it's actually a ...
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1answer
67 views

Why won't the bandstop filter work in this circuit?

This is the EMG circuit I designed. The cut off frequency of the bandpass is 20-3k Hz. This somehow worked already. But the bandstop filter doesn't show. Why is this? This is the freq-vout graph and ...
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1answer
65 views

Is this design of a charge amplifier for a piezoelectric sensor correct?

This is the specifications that must be met: "Design a charge amplifier for a piezoelectric sensor that has 500 pF capacitance. It should pass frequencies from 0.05 to 100 Hz so that it can ...
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1answer
38 views

Did I interpret these multisim results correctly?

From the circuit above, this is what I have to do: " Connect the circuit with R3 equal to 470 kΩ. Set the input frequency to 100 Hz. Adjust the signal level to get an output of 5 Vp-p. Record ...
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1answer
73 views

How to compute for the capacitor to achieve a certain cut-off frequency?

This is my task : "Select new values for C1 and C3 to get a lower cutoff frequency in the circuit shown above that is less than 20 Hz." What I did first was choose 15Hz and then computed for ...
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1answer
64 views

I need help deriving the cutoff frequency of a negative feedback amplifier

I have the question and answer below for deriving the closed-loop cutoff frequency of a feedback amplifier circuit. I can follow the working out all the way until the last 2 lines, where the writer ...
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Gain error calculation for op-amp circuit in inverting configuration

For an inverting op-amp, calculate minimum gain that is required for the op-amp to achieve a gain error of 1%, if the required closed-loop DC gain is -9. If the input resistance R1 is 1Kohm,find the ...
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3answers
80 views

Summing Integrator cut off

I would like to know how to calculate cut off frequency of this summing integrator circuit. I fail to find anywhere on the internet how to calculate cut off frequency in this configuration. Then how ...
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2answers
88 views

My simulated coax cut off frequency is way far off the calculated value

I used the lumped model to model a coax cable as a low pass filter in MATLAB. I also included ESR which is supposed to resemble the dielectric losses. I derived my transfer function from the circuit ...
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How to get lower cutoff frequency?

These are the equations for finding lower cutoff frequencies for a BJT common emitter amplifier: In finding the cutoff frequency, capacitor impedance must match the resistance so that output voltage ...
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1answer
67 views

Higher cutoff frequency of op-amp circuit is different in simulation and on paper

I have the circuit below: This is an inverting amplifier, the op-amp that is used is 741 as shown in the circuit. Open-loop gain of the op-amp is \$ A_{0}=2\times 10^5 \$ and the cutoff frequency of ...
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3answers
122 views

Cascade amplifiers with different corner frequency

In these 2 cases I have the output of a non inversor circuit connected to the input of an inversor circuit. The only difference is the resistors. What I have noticed is that the cutoff frequency is ...
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2answers
82 views

How to find the cutoff frequency using Simulink (from the scope)?

R=1000 ohm C=0.1uF I need to find the cutoff frequency from the scope and to show it matches the theory \$f= \frac{1}{2pi*RC}\$ In this case it's 1591Hz. How do I measure it?
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1answer
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Frequency dependent behavior of an inverting configuration of an opamp

I am a third-year chemistry student. I have essentially the understanding of a second-semester physics student when it comes to circuitry and electrical engineering. For reference, I know what gain is ...
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3answers
306 views

How to find the cutoff frequency of an underdamped second order lowpass filter

I've learned that for a first order LPF the 3dB frequency is one where the amp's gain is (surprise) -3dB below the DC gain. However, on a second order LPF that is underdamped we get a "peak" at around ...
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3answers
91 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 ...
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2answers
318 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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1answer
63 views

Open-source DIY audio spectrum analyser and/or graphic equaliser

does anyone know of any OpenSource/DIY audio spectrum analyser projects can they direct me to an article, video, pics hackaday and instructionals style also I.C's old or new that i could/should try ...
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1answer
161 views

In an inverting amplifier configuration why does do the gain resistors affect the circuit's frequency response if their ratio stays consistent?

I've been learning more about the characteristics of op amps and I found in a non-inverting amplifier simulation that the gain of an inverting op amp falls off as frequency increases. This behavior is ...
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2answers
77 views

How to calculate RC (in 2st RC lpf) that satisfies fc in real circuit

I'm designing a two-stage RC LPF (Low-Pass Filter) and I want a cutoff frequency \$f_c=1000\mathrm{Hz}\$. So, I choose \$R_1=3\mathrm{k\Omega}, R_2=33\mathrm{k\Omega}, C_1=4.7\mathrm{nF}, C_2=47\...
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46 views

Finding cut off frequency at - 3dB

I am a little bit stuck in finding the cut off frequency of high pass filter. Can someone confirm to me that this is the formula I should use: I have a transfer function H(p/w0), and to find it I'm ...
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92 views

3-dB frequency of cascaded opamps

We have two identical opamps with a first order low-pass response. They both have the same 3-dB frequency \$f_1\$. I need to show that their combined 3-dB frequency (when they are put in cascade) is: ...
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BJT low frequency analysis

I have a little bit of confusion on how the textbook author is determining the low frequency cutoffs for the 3 high pass filter components of this circuit: For the capacitor Cs, he finds Zi which is ...
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1answer
66 views

Cutoff frequency of class A common-emitter amplifier

I'm trying to understand the operation of a class A common-emitter amplifier, but I'm struggling to understand how the equivalent resistance for the cutoff frequency of C1 is determined. I also can't ...
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4k views

Why do microwave ovens use magnetrons?

With a lot of advancement in solid state electronics and signal manipulation, isn't it easier to simply take high amplitude signals with frequencies near 1 MHz and multiply the signals using diodes ...
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65 views

How to design a high pass filter given a stopband and cutoff frequency? [duplicate]

I have fs = 132 Hz and fc = 770 Hz I want to design a first order high pass filter that increases gain at a rate of 20dB per decade from 132 Hz until 770 Hz. Before 132 Hz the filter must stay ...
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1answer
85 views

Finding a gain bandwidth product using a test frequency

For GBP datasheet parameters of Op-amps, I have seen datasheets with test conditions like gain and Rl, but there are also datasheets with ftest as their conditions. How do we calculate the GBP of the ...
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1answer
74 views

Variable Frequency-Response analysis (amplifier)

I'm trying to understand what the book "Basic Engineering Circuit Analysis" by Irwin is saying at the chapter of variable frequency... It's trying to amplify a signal from 50Hz to 20000Hz. Where it ...
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3answers
563 views

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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1answer
102 views

How to determine the best resistance for a weak signal Twin-T notch filter?

I am designing a 50/60 Hz Twin-T notch filter for a weak (biomedical) signal output from an instrument amplifier (InAmp) to be chained to another active low pass ...
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1answer
101 views

Regards Band Pass Filter with AmpOp

I've tried to solve this contest question regards the band pass filter (find the frequency at low-pass and high-pass filters) the picture below: My attempt: I consider that the first stage is 2 low-...
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1answer
168 views

Does a low-pass filter average the higher-order frequencies into a “DC offset”?

In a Pound-Drever-Hall lock, an electronic signal is produced of the form: We are interested in electronically isolating the term: My question is: how can we filter to get exactly this term (listed ...
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Signal Attenuation TVS and series resistor

This question is in regards to signal attenuation on high speed data lines like RS-485 (and any others as well). I'm new to the signal world, so please bear with me here. Are there some useful ...
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1answer
811 views

Common mode choke parameters CAN circuitry - split termination concept

I am trying to the understand the important parameters of a common mode choke that will be placed at the CANL and CANH lines of a transceiver. First parameter: Impedance as function of frequency - I'...
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3answers
718 views

(Lack of) Miller Effect in Cascode considering Common Emitter and Common Base Seperately

I'm currently working on an analysis of a standard Cascode circuit, in particular why the frequency response is so good as it reduces the miller effect. I have had a very vague explanation given to ...
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3answers
135 views

Skewed frequency response of RLC circuit

I built a simple RLC circuit: I'm using a signal generator as input, and I'm reading the voltage across the capacitor with an oscilloscope. I've calculated that the resonant frequency (where I will ...
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1answer
55 views

What happens to the low cut off frequency when replaced with a larger bypass capacitor?

When the emitter capacitance is increased to 100 microfarads. What would happen to the low frequency cut off of this amplifier?
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Second Order Passive RC Low Pass Filter Doesn't Have -6dB at cutoff Frequency in LTSpice

For Second-Order RC filter the cutoff frequency is: $$fc = \frac{1}{2\pi \sqrt {R_1C_1R_2C_2}}$$ I have taken R1 = R2 = R = 1K Ohm and C1 = C2 = C= 0.1591 micro Farad. So the cutoff frequency comes ...
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1answer
203 views

Simple op-amp frequency response

In my textbook, there are two interrelated equations. 1. wb = wt / (1 + R2/R1) 2. wb = wt / Ao where ...
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2answers
64 views

Behavior of frequency in a sinusoidal circuit

My question is in regards to a circuit like this with a sinusoidal voltage source Vin. When I try to figure out the voltage ratio between Vin and Vout I get ωCR/(ωCR - j). I then try to ...
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70 views

Scaling of magnetic field strength and flux density measurements and shape of hysteresis loop

Note: this is part of a larger question which I was asked to separate into subquestions. Other subquestions: 1 and 2 I'm using the method outlined here to measure the induced magnetic flux density in ...
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116 views

Cutoff frequency of passive RC integrator used to measure magnetic flux density

Note: this is part of a larger question which I was asked to separate into subquestions. Other subquestions: 1 and 2 I am using a passive RC integrator to measure the induced magnetic flux density in ...