Notch Frequency
f = 1 / (2π√(LC))
Quick answer
This calculator solves f = 1 / (2π√(LC)) for Notch Frequency. With Inductance 10 mH, Capacitance 100 nF, the result is 5.033 kHz. It solves in 3 directions, so you can enter the values you have and get the one you need.
Calculator
Formula
Description
A notch (band-stop or band-reject) filter blocks a narrow range of frequencies centered at the notch frequency while passing all others. The center frequency is determined by the LC resonance, using the same formula as the resonant frequency calculator. At this frequency, the series LC branch has zero impedance (short circuit) or the parallel LC branch has infinite impedance (open circuit), depending on the topology. Notch filters are used to remove specific interference frequencies, such as 50/60 Hz power line hum in audio systems or specific carrier frequencies in communication systems.
Variables
- f — Notch center frequency (Hz)
- L — Inductance (H)
- C — Capacitance (F)
Practical Notes
The Twin-T RC notch filter is a popular active implementation that does not require an inductor. It uses three resistors and three capacitors arranged in two T-networks. The depth of the notch depends on component matching: 1% tolerance components can achieve 30-40 dB rejection. Digital notch filters (IIR or adaptive) can achieve 60+ dB rejection and can track varying interference frequencies.
Symbols and units
| Symbol | Meaning | Default unit | Accepted units |
|---|---|---|---|
| f | Notch Frequency | kHz | Hz, kHz, MHz, GHz |
| L | Inductance | mH | nH, µH, mH, H |
| C | Capacitance | nF | pF, nF, µF, mF, F |
Step by step
- 1. What you know: Inductance 10 mH, Capacitance 100 nF
- 2. The relation: f = 1 / (2π√(LC))
- 3. Substitute: L = 10 mH, C = 100 nF
- 4. Result: Notch Frequency = 5.033 kHz
Worked examples
Minimum range
Given: Inductance 100 µH, Capacitance 100 pF
Result: Notch Frequency = 1.592 MHz
Low range
Given: Inductance 1 mH, Capacitance 1 nF
Result: Notch Frequency = 0.1592 MHz
Typical
Given: Inductance 10 mH, Capacitance 100 nF
Result: Notch Frequency = 5.033 kHz
High range
Given: Inductance 100 mH, Capacitance 1 µF
Result: Notch Frequency = 0.5033 kHz
Maximum range
Given: Inductance 1 H, Capacitance 10 µF
Result: Notch Frequency = 50.33 Hz
Solving for each variable
Solve for Notch Frequency
Inductance 100 µH, Capacitance 100 pF → 1.592 MHz
Solve for Inductance
Notch Frequency 100 Hz, Capacitance 100 pF → 25330 H
Solve for Capacitance
Notch Frequency 100 Hz, Inductance 100 µH → 25.33 mF
How Notch Frequency changes with Inductance
| Inductance (input) | Notch Frequency (result) |
|---|---|
| 1 mH | 15.92 kHz |
| 2.5 mH | 10.07 kHz |
| 5 mH | 7.118 kHz |
| 7.5 mH | 5.812 kHz |
| 10 mH | 5.033 kHz |
| 15 mH | 4.109 kHz |
| 20 mH | 3.559 kHz |
| 40 mH | 2.516 kHz |
| 70 mH | 1.902 kHz |
| 100 mH | 1.592 kHz |
The same result in other units
| Unit | Value |
|---|---|
| Hz | 5033 |
| kHz | 5.033 |
| MHz | 0.005033 |
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<p><a href="https://vbatpower.com/formulas/notch-freq/">Notch Frequency</a> Calculator by vbatpower.com</p>Frequently asked questions
How do you calculate Notch Frequency?
Use f = 1 / (2π√(LC)). With Inductance 10 mH, Capacitance 100 nF, Notch Frequency works out to 5.033 kHz.
What is the formula for Notch Frequency?
The formula is f = 1 / (2π√(LC)). A notch (band-stop or band-reject) filter blocks a narrow range of frequencies centered at the notch frequency while passing all others.
How do you find Inductance when you know the other values?
Rearrange for Inductance: with Notch Frequency 100 Hz, Capacitance 100 pF, Inductance is 25330 H.
How do you find Capacitance when you know the other values?
Rearrange for Capacitance: with Notch Frequency 100 Hz, Inductance 100 µH, Capacitance is 25.33 mF.
What units does Notch Frequency use?
Notch Frequency is shown in Hz, kHz, MHz. Values are held in SI base units internally, so you can mix prefixes without converting by hand.
Related Concepts
All Filters formulas →Need more features?
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