OpFil uses an advanced DOS-based windowing system. The program runs well under all Windows versions. Originally selling for well over $1000 US, Schematica is now offering OpFil for $49 US when purchased alone, and for $29 US when purchased with either Filter Wiz LE or PRO (a savings of over 40%). OpFil's passive (and active) filter design capability complements the superb active filter design capability of Filter Wiz.

Features:
4 Approximations (Butterworth, Chebyshev, Inverse Chebyshev and Elliptic)
lowpass, highpass, bandpass and bandstop in both RLC and active-RC implementation
pole-zero locations and biquadratic coefficients group delay equalization using allpass filter stages