Cutoff Frequency Calculator

Circuit Type:

Resistance (R):

Capacitance (C):

Cutoff Frequency (Hz): Cutoff Frequency (kHz): Cutoff Frequency (MHz):

1. What is a Cutoff Frequency Calculator?

Definition: This calculator computes the cutoff frequency of RC and RL filter circuits, which is the frequency at which the output signal power drops to half its input value (-3 dB point).

Purpose: It is used in electronics to design filters that allow certain frequencies to pass while attenuating others, critical for audio systems, signal processing, and communication devices.

2. How Does the Calculator Work?

The cutoff frequency is calculated using:

For RC:

f_{c} = \frac{1}{2 π R C}

For RL:

f_{c} = \frac{R}{2 π L}

Where:

$f_{c}$ is the cutoff frequency (Hz)
$R$ is the resistance (Ω)
$C$ is the capacitance (F)
$L$ is the inductance (H)

Steps:

Select the circuit type (RC or RL)
Enter the resistance ( $R$ ) and select a unit (Ω, kΩ, MΩ)
For RC: Enter the capacitance ( $C$ ) and select a unit (pF, nF, µF, mF, F)
For RL: Enter the inductance ( $L$ ) and select a unit (nH, µH, mH, H)
Convert values to base units (Ω, F, H)
Calculate the frequency using the appropriate formula
Display results in Hz, kHz, and MHz

3. Importance of Cutoff Frequency Calculation

Details: The cutoff frequency defines the boundary between a filter’s passband and stopband, essential for designing low-pass, high-pass, or band-pass filters used in audio equipment, radio receivers, and noise reduction systems.

4. Using the Calculator

Tips: Enter the resistance and either capacitance (for RC) or inductance (for RL) with their units. The calculator computes the cutoff frequency in Hz, kHz, and MHz, with 5 decimal places or scientific notation for extreme values (>10000 or <0.0001).

Examples:

RC: $R = 1 kΩ$ , $C = 100 nF$ :
- $f_{c} = \frac{1}{2 π \times 1000 \times 10^{- 7}} = 1591.54943 Hz$
- kHz = 1.59155, MHz = 0.00159
RL: $R = 10 Ω$ , $L = 1 mH$ :
- $f_{c} = \frac{10}{2 π \times 0.001} = 1591.54943 Hz$
- kHz = 1.59155, MHz = 0.00159

5. Frequently Asked Questions (FAQ)

Q: What is cutoff frequency?
A: It’s the frequency where a filter begins to significantly attenuate the signal, typically at -3 dB (half power).

Q: How does RC differ from RL?
A: RC filters use a resistor and capacitor (low-pass or high-pass), while RL filters use a resistor and inductor (typically high-pass).

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