Digital to analog converter (D \ A conversion) is an important interface processing, the digital signal into an analog signal which will drive the external device.

In this example D \ A converter using the ratio method of the adder. Input resistor value of the adder represents the binary input code heavy weight.

Circuit

curve

V=-（0*(1000/1000)+1*(1000/2000)+0*(1000/4000)+1*(1000/8000)）

  = -(1/2+1/8)

  = -0.625

program

model cb

  Modelica.Electrical.Analog.Basic.Ground ground1 annotation(

    Placement(visible = true, transformation(origin = {-92, 2}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));

  Modelica.Electrical.Analog.Ideal.IdealizedOpAmpLimted idealizedOpAmpLimted2 annotation(

    Placement(visible = true, transformation(origin = {16, -40}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));

  Modelica.Electrical.Analog.Basic.Ground ground5 annotation(

    Placement(visible = true, transformation(origin = {58, -74}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));

  Modelica.Electrical.Analog.Sources.ConstantVoltage constantVoltage5(V = -15) annotation(

    Placement(visible = true, transformation(origin = {26, -64}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));

  Modelica.Electrical.Analog.Basic.Ground ground6 annotation(

    Placement(visible = true, transformation(origin = {-48, -56}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));

  Modelica.Electrical.Analog.Basic.Resistor resistor1(R = 1000)  annotation(

    Placement(visible = true, transformation(origin = {30, 22}, extent = {{-10, -10}, {10, 10}}, rotation = 180)));

  Modelica.Electrical.Analog.Sources.ConstantVoltage constantVoltage1(V = 15) annotation(

    Placement(visible = true, transformation(origin = {26, -10}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));

  Modelica.Electrical.Analog.Basic.Ground ground2 annotation(

    Placement(visible = true, transformation(origin = {60, -20}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));

  Modelica.Electrical.Analog.Interfaces.Pin pin annotation(

    Placement(visible = true, transformation(origin = {99, -41}, extent = {{-3, -3}, {3, 3}}, rotation = 0), iconTransformation(origin = {99, -41}, extent = {{-3, -3}, {3, 3}}, rotation = 0)));

  Modelica.Electrical.Analog.Basic.Resistor resistor2(R = 8000) annotation(

    Placement(visible = true, transformation(origin = {-34, 26}, extent = {{-10, -10}, {10, 10}}, rotation = 180)));

  Modelica.Electrical.Analog.Basic.Resistor resistor3(R = 4000) annotation(

    Placement(visible = true, transformation(origin = {-34, 10}, extent = {{-10, -10}, {10, 10}}, rotation = 180)));

  Modelica.Electrical.Analog.Basic.Resistor resistor4(R = 2000) annotation(

    Placement(visible = true, transformation(origin = {-34, -6}, extent = {{-10, -10}, {10, 10}}, rotation = 180)));

  Modelica.Electrical.Analog.Basic.Resistor resistor5(R = 1000) annotation(

    Placement(visible = true, transformation(origin = {-34, -22}, extent = {{-10, -10}, {10, 10}}, rotation = 180)));

  Modelica.Electrical.Analog.Sources.ConstantVoltage constantVoltage2(V = 1) annotation(

    Placement(visible = true, transformation(origin = {-78, 26}, extent = {{10, -10}, {-10, 10}}, rotation = 0)));

equation

  connect(idealizedOpAmpLimted2.in_p, ground6.p) annotation(

    Line(points = {{6, -46}, {-48, -46}, {-48, -46}, {-48, -46}}, color = {0, 0, 255}));

  connect(pin, idealizedOpAmpLimted2.out) annotation(

    Line(points = {{100, -40}, {26, -40}, {26, -40}, {26, -40}}, color = {0, 0, 255}));

  connect(resistor5.n, ground6.p) annotation(

    Line(points = {{-44, -22}, {-48, -22}, {-48, -46}, {-48, -46}, {-48, -46}}, color = {0, 0, 255}));

  connect(resistor3.n, ground6.p) annotation(

    Line(points = {{-44, 10}, {-48, 10}, {-48, -46}, {-48, -46}, {-48, -46}}, color = {0, 0, 255}));

  connect(resistor4.n, constantVoltage2.p) annotation(

    Line(points = {{-44, -6}, {-68, -6}, {-68, 26}, {-68, 26}, {-68, 26}}, color = {0, 0, 255}));

  connect(resistor2.n, constantVoltage2.p) annotation(

    Line(points = {{-44, 26}, {-68, 26}, {-68, 26}, {-68, 26}}, color = {0, 0, 255}));

  connect(constantVoltage2.n, ground1.p) annotation(

    Line(points = {{-88, 26}, {-92, 26}, {-92, 12}}, color = {0, 0, 255}));

  connect(resistor2.p, idealizedOpAmpLimted2.in_n) annotation(

    Line(points = {{-22, 26}, {-4, 26}, {-4, -34}, {8, -34}, {8, -34}}, color = {0, 0, 255}));

  connect(resistor3.p, idealizedOpAmpLimted2.in_n) annotation(

    Line(points = {{-22, 10}, {-4, 10}, {-4, -34}, {8, -34}, {8, -34}}, color = {0, 0, 255}));

  connect(resistor4.p, idealizedOpAmpLimted2.in_n) annotation(

    Line(points = {{-22, -6}, {-4, -6}, {-4, -34}, {8, -34}, {8, -34}, {8, -34}}, color = {0, 0, 255}));

  connect(resistor5.p, idealizedOpAmpLimted2.in_n) annotation(

    Line(points = {{-22, -22}, {-4, -22}, {-4, -34}, {8, -34}, {8, -34}, {8, -34}}, color = {0, 0, 255}));

  connect(idealizedOpAmpLimted2.out, resistor1.p) annotation(

    Line(points = {{26, -40}, {78, -40}, {78, 22}, {40, 22}, {40, 22}, {40, 22}}, color = {0, 0, 255}));

  connect(resistor1.n, idealizedOpAmpLimted2.in_n) annotation(

    Line(points = {{22, 22}, {8, 22}, {8, -34}, {8, -34}, {8, -34}}, color = {0, 0, 255}));

  connect(idealizedOpAmpLimted2.s_n, constantVoltage5.p) annotation(

    Line(points = {{18, -50}, {18, -50}, {18, -64}, {18, -64}}, color = {0, 0, 255}));

  connect(constantVoltage1.p, idealizedOpAmpLimted2.s_p) annotation(

    Line(points = {{16, -10}, {16, -10}, {16, -30}, {16, -30}}, color = {0, 0, 255}));

  connect(constantVoltage5.n, ground5.p) annotation(

    Line(points = {{36, -64}, {58, -64}, {58, -64}, {58, -64}}, color = {0, 0, 255}));

  connect(ground2.p, constantVoltage1.n) annotation(

    Line(points = {{60, -10}, {36, -10}, {36, -10}, {36, -10}}, color = {0, 0, 255}));

  annotation(

    uses(Modelica(version = "3.2.2")),

    experiment(StartTime = 0, StopTime = 1, Tolerance = 1e-06, Interval = 0.0002));

end cb;