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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29 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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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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1answer
58 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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25 views

Cutoff frequency of Common mode part of EMI Filter?

Anybody knows how we can determine the cutoff frequency for the common mode parts of EMI Filter? I know for the differential mode we use FFT to find the highest harmonics of input current and then ...
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1answer
38 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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3answers
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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57 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
51 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
65 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
205 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
72 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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250 views

Calculating cutoff frequency of a second order active filter

I'm trying to calculate cutoff frequency of the low pass filter that schematic is shown below. I obtained this circuit from Analog Filter Wizard and it's cutoff frequency is 170kHz at -3 dB, but when ...
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1answer
78 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
156 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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0answers
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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
405 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
357 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
95 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
52 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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2answers
2k views

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
133 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
56 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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0answers
58 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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0answers
68 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 ...
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2answers
334 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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0answers
50 views

determine the cutoff frequency of a nMOS in common gate with gate resistance

I have to determine the upper cutoff frequency of this circuit. I absolutely mustn't use the laplace domain because it's too time consuming so not compatible with the time I have at the exam. A rapid ...
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1answer
260 views

Common source amplifier, source degeneration and determining the cutoff frequency

I have a n-MOS transistor with the following biasing network: I have to determine the cutoff frequency due to GS and GD capacitances The method used by my book is to first redefine the ...
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3answers
3k views

How do we define the cutoff frequency in an active Op-Amp filter?

When we get a circuit such as the following: How do we define the cut-off frequency? Is it still $$f_c = \frac1{2\pi R_1C_1}$$ since \$f_c\$ is defined for \$X_{c1} = R_1\$? Or is it defined so that \...
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2answers
3k views

How to calculate amplifier gain (in dB) using frequency?

I know how to calculate decibel gain using the ratio of power, or Vin/Vout. However, is there a way to calculate the magnitude of the attenuation and phase angle when you’re given the cutoff ...
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2answers
2k views

How to choose a cut-off frequency by interpreting FFT

I have a question concerning low pass filtering of IMU acceleration and gyro data. To choose a reasonable cut-off frequency, I thought about making some observations in the spectrum. Now I have some ...
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0answers
84 views

Roll-off of a third-order active filter [duplicate]

I've a third order active filter, without zeros. I know that when \$f=0\$ the gain response is \$1\$. So the cutoff-frequency is located at: $$\left|\text{H}\left(\omega_0\right)\right|=\frac{1}{\...
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Cut-off frequency calculation

Can anyone calculate the cut-off frequency and tell me which formula to be used on the Positive end of OPAMP? what is the role of R1 here and R7 from the feedback? Please answer in details with ...
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1answer
65 views

i want to know the cut off frequency on the 2 OPAMPS … Do I take 6K resistor and 5K resistor for OPAMP#2

I hope some one can check, I have a signal coming from a source and it goes in to 2 OPAMPS, and both has to be checked for cutoff frequencies... I know 1/2*pi*RC is the formula but my question is how ...
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1answer
104 views

frequency response multistage

hello every one i need ask about frequency response i have an old question of our professor exam in few year, and i try to solve this question many time but i can't so please if any one have idea ...
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1answer
321 views

MOS Amplifier Circuit - Lower 3dB Frequency Calculation

I am confused with the above problem as the output node is not specified. If the output node is drain, it will be common source and if output is source, then it will be common drain. My question is ...
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1answer
8k views

Derivation of cutoff frequency and phase shift for RC low pass filter

I've been having some problems with how to find the cutoff frequency and the phase shift for a simple RC low pass filter circuit. I've read this post, but I need a better understanding of what ...
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1answer
105 views

Which cut off frequency I should use in order to cancel AC noise with the low pass filter?

it may sound a bit stupid, but the thing is that I want to cancel the noise caused by AC frequencies in a circuit. I know I have to use a low pass filter, but which cut-off frequency should I use? I'...
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6answers
701 views

Can a filter change the frequency of the input signal?

I am given a square wave with Vmin = 0V and Vmax=5V , T(period)=8ms and duty cycle 25%. I am asked to find the properties(low cutoff , high cutoff , bandwidth) of a band pass filter that will make the ...
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1answer
387 views

Calculating cutoff frequency of RCL circuit

Given is this circuit: I know that: $$G(j\omega)=\frac{\frac{1}{j\omega C}}{j\omega L+\frac{1}{j\omega C}+R}$$ But how do I calculate from this my cutoff frequency?
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1answer
1k views

Significance of cut-off frequency in a low-pass filter

My question is: why do we choose cut-off frequency to satisfy that the magnitude of transfer function \$ H(\omega) = \frac{1}{\sqrt{2}} \$? Therefore I am not asking how cut-off frequency is ...
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2answers
191 views

Calculating the cut off frequency of a electronic filter

I've the following circuit: I know that the transfer function is given by: $$\mathscr{H}\left(\text{s}\right)=\frac{1}{1+sb_1+s^2b_2+s^3b_3}\tag1$$ Now, in this post they say that I can find the ...
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1answer
556 views

RC circuit and bessel filter finding the cutoff frequency

I've the following filer circuit and I want to know if my analysis is right. simulate this circuit – Schematic created using CircuitLab Using the transfer function of a series RC circuit: $$\...
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2answers
829 views

20 Hz subsonic 350 W RC low pass filter

I build rotary subwoofers that produce ULF (subsonic) sound levels (youtube) . The amplifier that I use is 12V 350W and supplies up to 25 amps. I would like to create a reasonably high quality, ...
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2answers
1k views

High pass filter attenuating frequencies equal to cutoff frequency

I'm developing a HPF to attenuate frequencies below 30KHz. My input voltage is a sinusoidal voltage from 0V to + 5V with a frequency of 30KHz. My objective is to attenuate frequencies below 30KHz ...
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1answer
398 views

First order filter cut off frequency

Hi, I have been asked to estimate the half-power cutoff frequency of a first order filter that gave this response to a step input. The problem I am having is I have only ever been given examples with ...
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1answer
983 views

UK Mains Frequency Limits

Question Is there a maximum limit to mains frequency range that appliances will accept (e.g. if they conform to UK or EU standards?) e.g. The Dynamic Demand web site indicates that there is a legal ...
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2answers
1k views

2nd order passive low pass filter cutoff frequency with additional paralel resistor before the second capacitor

How we can calculate the transfer function and cutoff frequency for this type of filter? For second order low pass filter the natural frequency is: $$ f_n = \frac{1}{2\pi \sqrt{R_1 R_2 C_1 C_2}} $...
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1answer
137 views

how can I calculate the cutoff frequency for this low pass filter?

simulate this circuit – Schematic created using CircuitLab
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1answer
401 views

How is definition of cutoff frequency consistent with KVL?

Low pass and high pass \$RC\$ filters have a cutoff frequency that is equal to $$f_c=\frac{1}{2\pi RC}$$ This should be the frequency at which the ratio \$|V_{out}/V_{in}|\$ is equal to \$1/\sqrt{2}\$....