// VerilogA for mrModels, mr_pas_r_va, veriloga

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

module mr_pas_r_va(P1, P2);
    inout P1, P2;
    electrical P1, P2;

    // =================================== Parameters ===================================
    parameter real R = 1000.0 from (0:inf); // Resistance in Ohms
    parameter real TC1 = 0.0;               // Linear temperature coefficient (1/°C)
    parameter real TC2 = 0.0;               // Quadratic temperature coefficient (1/°C²)

    // ======== Flicker (1/f) noise parameters (optional - set Kf=0 to disable) =========
    parameter real Kf = 0.0;                // Flicker noise coefficient (1e-11 to 1e-9)
    parameter real Af = 1.0;                // Flicker noise exponent (usually 1.0)    

    real R_eff;                             // Effective resistance after temp coeff
    real T;                                 // Temperature in Kelvin

    analog begin
        T = $temperature;                   // Get simulation temperature (Kelvin)

        // Effective resistance with temperature dependence
        R_eff = R * (1 + TC1*(T - 300.15) + TC2*(T - 300.15)*(T - 300.15));

        // Ohm's law
        V(P1, P2) <+ R_eff * I(P1, P2);

        // ============================ Thermal (white) noise ===========================
        // Correct formula: voltage noise power = 4 * k * T * R
        V(P1, P2) <+ white_noise(4 * `P_K * T * R_eff, "thermal");

        // ======================== Optional flicker (1/f) noise ========================
        // Excess noise that appears in some real resistors (carbon, thick film, etc.)
        if (Kf > 0) begin
            // Current noise contribution (common way to model resistor excess noise)
            V(P1, P2) <+ flicker_noise(Kf * pow(abs(I(P1,P2)), Af), 1.0, "excess");
        end
    end
    
endmodule