// Low Pass filter model based on -3dB frequency definition
// Author: A. Sidun
// Source: AnalogHub.ie

`include "constants.vams"
`include "disciplines.vams"

module LPF(in, out);
electrical in, out;
parameter real Cutoff_frequency = 10k;      // -3dB frequency
parameter real Filter_Order = 1;            // 1 for 20dB/dec, 2 for 40dB/dec

analog begin
case (Filter_Order)
1: begin    // First Order LPF (-20dB/dec)
	V(out) <+ laplace_nd(V(in),{2*`M_PI*Cutoff_frequency},{2*`M_PI*Cutoff_frequency, 1});
	V(out) <+ laplace_nd(V(in),{2*`M_PI*Cutoff_frequency},{2*`M_PI*Cutoff_frequency, 1});
    end

2: begin    // Second Order LPF (-40dB/dec)
	V(out) <+ laplace_nd(V(in),{(2*`M_PI*Cutoff_frequency)**2},{(2*`M_PI*Cutoff_frequency)**2, 4*`M_PI*Cutoff_frequency,1});
    end
endcase
end
endmodule