What is Cutoff frequency: Definition and 17 Discussions

In physics and electrical engineering, a cutoff frequency, corner frequency, or break frequency is a boundary in a system's frequency response at which energy flowing through the system begins to be reduced (attenuated or reflected) rather than passing through.
Typically in electronic systems such as filters and communication channels, cutoff frequency applies to an edge in a lowpass, highpass, bandpass, or band-stop characteristic – a frequency characterizing a boundary between a passband and a stopband. It is sometimes taken to be the point in the filter response where a transition band and passband meet, for example, as defined by a half-power point (a frequency for which the output of the circuit is −3 dB of the nominal passband value). Alternatively, a stopband corner frequency may be specified as a point where a transition band and a stopband meet: a frequency for which the attenuation is larger than the required stopband attenuation, which for example may be 30 dB or 100 dB.
In the case of a waveguide or an antenna, the cutoff frequencies correspond to the lower and upper cutoff wavelengths.

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  1. I

    Cutoff frequency for this RLC circuit

    How would i find the cut of frequency of this RLC circuit .I have used LTspice to find it but what is the equation for finding it
  2. tworitdash

    What is the attenuation below cut-off frequency for TE10?

    It is not useful to talk about the attenuation below cut-off frequency, but I have this doubt about what happens to the wave below cut off for an electric conductor. As we know if we derive the propagation constant, it becomes imaginary saying that there should not be any wave propagating in the...
  3. D

    B Photoelectric Effect under cutoff frequency

    I understand the concepts of photoelectric effect where an electron will be emitted when a photon with sufficient energy collides with it. There are two parts to this question, 1. What happens during the collision? Is the photon absorbed by the photoelectron wholly as energy? 2. If so...
  4. W

    Calculate attenuation constant of an aperture

    Homework Statement The shielding efficiency of an aperture depends on e−αd, where α is the frequency-dependent attenuation constant of the aperture and d is the thickness of the material (or the cutoff waveguide) at frequencies below cutoff. where ωc=2πfc. Calculate α for an air-vent...
  5. Y

    Derivation of cutoff frequency for RC circuit?

    How is it derived? The cutoff frequency is Fc = 1/2piRC. R = resistance, C = capacitance. I read somewhere it has to do with Laplace Transforms, but I'm not sure where to go from here. It kind of irks me to just accept this equation without some proof. Thanks!
  6. S

    Maximum (cutoff) freq for a photoresistor

    Hi, I am working on a project where I want to use a photoresistor to measure displacement, by reflecting light off of a small component and measuring the light that is reflected. the goal is to measure vibration. I am having a hard time finding information on the cutoff frequencies of...
  7. P

    How to test cutoff frequency of IR filter on camera?

    Modern cell phones seems to come with IR filters on their cameras. I want to do an experiment to figure out what wavelengths these filters allow to pass and which they block. How would I go about doing this? Also, what sort of equipment would I need? I am a university student so I have access...
  8. B

    Cutoff frequency in this circuit

    I'd say that the cutoff frequency of the circuit in the following scheme is given by f_0=\frac{1}{2 \pi (R_1//R)C} but I don't know how to prove this idea.. Do you agree with me? what would you say? Many thanks!
  9. M

    Low-pass LC butterworth filter cutoff frequency question

    I am designing a 5-pole low-pass butterworth filter to have a cutoff frequency of ~50 Hz. It has a source impedance of ~1 Ohm, and a load impedance of ~50 Ohm (The load impedance can be changed around if that will help later). Because of these, I am using the "T" configuration. I used the table...
  10. H

    Understanding Cutoff Frequency & Time Domain: Help Needed

    Hi, I am trying to understand the impact of cut off frequency on the gain and trying to relate it in time domain but unable to do so. For e.g., I have built a single pole RC filter wherein R and C values are chosen to match the cut off frequency of 1K (R = 10KΩ/C = 16nF). The input is a square...
  11. P

    Inverting OP amp cutoff frequency

    Homework Statement 1. Using the LM324 op amp build an inverting amplifier with a gain of 50. Measure the cut-off frequency 2. Plot your results on a graph as a function of log(frequency). Comment on the results I have done this in a lab and then graphed it, it seems to be around...
  12. C

    Calculating the cutoff frequency on analog filter

    for Butterworth filter -> Ha(s).Ha(-s) where s=jΩ I got (Ω^4)/1+Ω^6 hence this not Butterworth filter, and I managed to find all the poles, where all the poles lie on the left hand side so this filter is stable.. My problem is, I'm not quite sure how to calculate the cutoff frequency, for...
  13. L

    Photoelectric effect and cutoff frequency

    Homework Statement I was just wondering that when I have a graph of the Stopping Potential versus Frequency of the light. How can I find the value for the cutoff frequency? Wavelength Vo 160 nm 2.99 V 53 nm...
  14. C

    Upper cutoff frequency for rectangular waveguide

    So I know there is an upper cutoff frequency (at least in the microwave band) for a rectangular waveguide. However for the life of me I can't find why one would exist in the equations, the internet is full of references to it based off of the dimensions of the waveguide, but I'm curious whether...
  15. E

    Kittel's Solid-State Physics: Finding Cutoff Frequency \omega_D

    Homework Statement This question refers to Kittel's solid-state physics book. Above equation (23), Kittel says that a cutoff frequency \omega_D is determined by (19) as" and then he gives equation (23). I have absolutely no idea where equation (23) comes from. Homework Equations...
  16. L

    Bremsstrahlung near the cutoff frequency, experimental data

    Goodmorning, I would be interrested in experimental data regarding the Bremsstrahlung process near the quantum mechanical cutoff, possibly single events data. I thought that maybe something like a bubble chamber picture could illustrate this process. This is maybe a naïve dream but this...
  17. B

    Help Needed: Low Pass Filter Cutoff Frequency Closest to 100 kHz

    hi there if anyone could help i would be very grateful for a low pass filter from the following list choose the two components which would produce a cut off frequency closest to 100 khz resistor capacitor 1.6 k ohm 1 nf 33 k ohm 330 nf 150 k ohm 10 uf...