library ieee;  use ieee.math_real.all;
use ieee.electrical_systems.all;

entity opamp_2pole_res is
  generic ( A : real := 1.0e6;	    -- open loop gain
            rin : real := 1.0e6;    -- input resistance
            rout : real := 100.0;   -- output resistance
            fp1 : real := 5.0;	    -- first pole
            fp2 : real := 9.0e5 );  -- second pole
  port ( terminal in_pos, in_neg, output : electrical );
end entity opamp_2pole_res;

----------------------------------------------------------------

architecture ltf of opamp_2pole_res is

  constant wp1 : real := fp1 * math_2_pi;
  constant wp2 : real := fp2 * math_2_pi;
  constant num : real_vector := (0 => wp1 * wp2 * A);
  constant den : real_vector := (wp1 * wp2, wp1 + wp2, 1.0);
  quantity v_in across i_in through in_pos to in_neg;
  quantity v_out across i_out through output;

begin

  i_in  == v_in / rin;  -- input current

  v_out == v_in'ltf(num, den) + i_out * rout;

end architecture ltf;