module lowpass_1(in,out);
 input in;
 output out;
 voltage in,out;

 parameter real freq_p1 = 1M from (0:inf),
                freq_p2 = freq_p1 from [freq_p1:inf);

 analog
   V(out) <+ laplace_nd(V(in), [1] ,
             [1,1/(`M_TWO_PI*freq_p1),pow(1/(`M_TWO_PI*freq_p2),2)] );

endmodule