# T Filter Calculator (with Examples)

A T-filter is used when the input impedance is low. It is an alternative to the very popular Pi filter.

This calculator below requires

• Cutoff Frequency (Fc)

## Example T Filter Calculation

For a source impedance of 50 Ω and a load Impedance of 1 kΩ, design a low pass filter with a cutoff frequency of 100 kHz.

Use the calculator above, the component values are as follows:

• L1 = 2.39 mH
• C2 = 2.12 nF
• L3 = 796 uH

We can also confirm that for the example in  where the source impedance is 50 Ω, load Impedance of 10 kΩ, cutoff frequency of 100 kHz, the calculator provides the following component values

• L1 = 23.9 mH
• C2 = 212 pF
• L3 = 7.96 mH

Used when either the input impedance is low or both input and output impedances are low

Uses two inductors instead of one as in the case of the Pi Filter. Inductors are more expensive than capacitors and therefore the Pi filter is preferred. Note that a Pi filter can be used when

• the input impedance is high
• both input and output impedances are high
• input and output impedances are equal

## References

  The Art of Electronics by Horowitz and Hill

## Related Calculators

• Pi Filter – includes four different calculators for both low pass and hi pass filters
• Power supply pi filters – for both equal and unequal impedance
• Filter Bandwidth – compute the bandwidth and center frequency from the start and stop frequencies. Useful when you look at the data sheets for SAW filters that don’t provide this info up front.
• Pi Filter Cutoff Frequency – Use the component values from a schematic to find the cutoff frequencies for both low and high pass filters
• CLC Filter – provides component values for a desired low pass frequency response