| 
  
  
                | Butterworth Pi LC High Pass Filter Calculator | | 
 |  |  |  |  |  | Enter value, select unit and click on calculate. Result will be displayed. |  
 
 |  | 
		The Butterworth type filter was first described by the British engineer Stephen Butterworth.
 | 
 
		A PI filter is a filter that has a series element and two parallel elements connected in the  
shape of the Greek letter PI.
 Butterworth filter are characterized by a constant gain (flat response) across the 
		midband of the circuit and a 20 dB per decade roll-off rate for each pole contained in the circuit.
 
 Butterworth filters are termed maximally flat magnitude response filters, optimized for gain flatness in the pass band. 
The attenuation is -3db at cutoff frequency. Above the cutoff frequency the attenuation is -20 db.
 
 The Butterworth is the only filter that maintains same shape for higher orders whereas other varieties of filters (Bessel,  
Chebyshev, elliptic) have different shapes at higher orders.
 
 A High pass filter is a filter that passes high frequencies, but attenuates  
frequencies lower than the cutoff frequency.
 
 |