Design your high pass filter circuit by selecting a filter type (RC, RL, or LC) and entering your component values. Input resistance, capacitance or inductance, and the tool calculates your -3dB cutoff frequency — plus shows the relationship between all three values so you can solve for any unknown.
Cutoff Frequency (-3dB)
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Resistance
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Capacitance
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Inductance
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Time Constant (τ)
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Angular Frequency (ω)
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A high pass filter is a circuit that allows signals above a certain cutoff frequency to pass through while attenuating (blocking) frequencies below that threshold. It's commonly used to remove low-frequency noise, hum, or DC offset from a signal — for example, removing rumble from audio or blocking DC bias in amplifier stages.
The cutoff frequency, also called the -3dB frequency, is the point at which the filter's output power drops to half of the input power (a gain reduction of approximately 70.7%). For frequencies above the cutoff, the high pass filter passes the signal with minimal attenuation. Below the cutoff, the signal is increasingly attenuated.
For a 1 kHz RC high pass filter using the formula fc = 1 / (2πRC), you can choose R = 1 kΩ and solve for C: C = 1 / (2π × 1000 × 1000) ≈ 159 nF. Alternatively, with R = 10 kΩ you'd need C ≈ 15.9 nF. Use standard capacitor values (like 150 nF or 220 nF) and adjust R accordingly.
An RC filter uses a resistor and capacitor — it's the most common, simple, and inexpensive choice. An RL filter uses a resistor and inductor — inductors are bulkier and more expensive but useful at higher frequencies. An LC filter uses an inductor and capacitor with no resistor — it has a sharper roll-off and is used where minimal signal loss is critical, such as in RF and power supply applications.
In an RC circuit, placing the capacitor in series with the signal path and the resistor to ground creates a high pass filter. Swapping their positions (resistor in series, capacitor to ground) makes a low pass filter. The key rule: a high pass filter passes high frequencies and blocks low ones, while a low pass filter does the opposite.
The cutoff frequency for an RC high pass filter is: fc = 1 / (2πRC), where R is resistance in ohms, C is capacitance in farads, and fc is the cutoff frequency in hertz. You can rearrange this to solve for R = 1 / (2πfcC) or C = 1 / (2πfcR).
For an RL high pass filter, the cutoff frequency is: fc = R / (2πL), where R is resistance in ohms and L is inductance in henries. You can rearrange to find R = 2πfcL or L = R / (2πfc).
For an LC high pass filter (lossless, no resistor), the resonant cutoff frequency is: fc = 1 / (2π√(LC)), where L is inductance in henries and C is capacitance in farads. LC filters provide a steeper roll-off than RC or RL filters and are widely used in RF and audio crossover circuits.