Recommended Free Tools
An RC filter’s cutoff is called the −3 dB point because, at that frequency, its output power is half the passband power. With the same impedance, that corresponds to an output voltage about 70.7% of the passband voltage—not 50%. The label marks a point on a gradual response curve, not a frequency where the filter suddenly stops working.
How the −3 dB value comes from half power
Decibels express ratios on a logarithmic scale. For power, the level change is 10 log10(Pout/Pin). At half power, this is 10 log10(1/2) = −3.0103 dB, conventionally rounded to −3 dB.
As an Amazon Associate I earn from qualifying purchases.
For voltage, the decibel formula is 20 log10(Vout/Vref). When the compared voltages are across equal impedances, power varies with voltage squared. Half power therefore means a voltage ratio of 1/√2, or about 0.707. The IEEE Technology Navigator describes the half-power point as an approximately 0.707 voltage ratio and a 3.01 dB drop: IEEE Technology Navigator.
Quick wins for a faster PC:
Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →That equal-impedance qualification matters: a voltage ratio does not by itself establish a power ratio if the impedances differ.
#1 Best Overall
- The item is New and good quality.
- Tested before shipping.
- ♥ Type:RC Filter♥ Weight:0.3kg (0.66lb.)
- Easy to use.
- Any question please contact me,have a nice day.
Where the corner occurs in a first-order RC low-pass
For an ideal, unloaded first-order low-pass with output taken across the capacitor, the transfer-function magnitude is |H(jω)| = 1/√(1 + (ωRC)2). At the corner, ωRC = 1, so the magnitude is 1/√2 of its passband value.
Since angular frequency ω = 2πf, the cutoff is fc = 1/(2πRC), or equivalently ωc = 1/RC. Microchip’s Bode Plot technical reference identifies this first-order RC relationship as the −3 dB point.
Rank #2
- Package Include: Glow Plug Ignitor (AA Battery Type), Charger(1), Fuel Bottle(1),Hex Crosses Wrench(2), Screw Drivers(2), Aluminum capped air filter w/ element(1)
What happens at and beyond cutoff
- At cutoff: The ideal first-order low-pass output is about 70.7% of its passband voltage; under equal-impedance comparison, its power is half. Its phase shift is −45°.
- Above cutoff: The low-pass continues to attenuate rather than switching off. Its ideal first-order magnitude response approaches a slope of −20 dB per decade.
- For a high-pass RC filter: The same half-power criterion is measured relative to the high-frequency passband, with the passband direction reversed.
Why a built circuit can differ from the simple formula
The expression fc = 1/(2πRC) assumes a simple first-order section that is not significantly loaded. Source resistance and the load connected to the output can change the effective circuit values and shift the observed corner. If a measured cutoff does not match the calculation, check the source and load impedances as well as the nominal resistor and capacitor values.
Outdated Drivers Are Slowing You Down
One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchWindows Errors? Fix Them Before They Spread
Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallWhat the −3 dB label does—and does not—tell you
The −3 dB convention gives a useful reference point, but a cutoff number alone does not describe an entire filter. When comparing designs, consider the required corner frequency, attenuation farther into the stopband (which depends on response and order), passband behavior, phase response, and the source and load impedances. Higher-order filter families may use other cutoff conventions or design definitions, so the −3 dB meaning should not be assumed without checking the specific response.
Quick Recap
Best Value
- Capacitance: 2200uF
- Voltage: 10 Volts
- Maximum Temperature: 105°C
- Manufacturer: Various
Rank #4
- absorption circuit module used on protecting the or thyristor because it can avoid amage that from inductive electromotive force generated by the inductive load when on or . Preventing electro interference and increasing the anti-jamming capability of the microcontroller.
- For or for C 5 ~ 400V inductive load (less than 1000W), for protection contacts or thyristor.
- absorption circuit,absorb induced electromotive force that from inductive load.
- With varistor, to prevent excessive fluctuations in voltage or current is too large and resulting in contact adhesion.
- To provide anti-interference ability of the circuit.
Rank #3
- Capacitance:10PF (100)
- Voltage resistance: 50V
- Pitch: 5.08mm，Installation method: in-line (2 feet)
- Monolithic capacitors are another name for multilayer ceramic capacitors, abbreviated as MLCCs.widely used in various military and civilian electronic machines and electronic equipment. Such as computers, telephones, program-controlled switches, sophisticated test equipment, radar communications, etc.
- Excellent Humidity Resistance, Miniature Size, Wide Capacitance, Reliable Performance,fast switching speed, large power dissipation and good current performance you need
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
