# 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### 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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### (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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### 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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### 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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### 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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### 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 ...