Add diode modeling function

include/ame.hpp

@@ -29,6 +29,7 @@
 #include "ame_Ambisonics.hpp"
 #include "ame_AudioBuffer.hpp"
 #include "ame_Biquad.hpp"
+#include "ame_Circuit.hpp"
 #include "ame_Conversion.hpp"
 #include "ame_DcBlock.hpp"
 #include "ame_Delay.hpp"

include/ame_Circuit.hpp

@@ -0,0 +1,28 @@
+/** 
+ Analog circuit modelings
+ @file ame_Circuit.hpp
+ @author Akiyuki Okayasu ([email protected])
+ @copyright Copyright (c) 2021 - Akiyuki Okayasu
+ 
+ AME is released under the MIT license.
+*/
+
+#pragma once
+
+#include <concepts>
+
+namespace ame
+{
+/** diode modeling.
+ https://jatinchowdhury18.medium.com/complex-nonlinearities-epsiode-2-harmonic-exciter-cd883d888a43
+
+ @param x 
+ @return FloatType
+ @note When the input is 1.0, the output is larger than 1.0 
+*/
+template <std::floating_point FloatType>
+inline FloatType diode (FloatType x)
+{
+ return static_cast<FloatType> (0.2) * (std::exp (x * static_cast<FloatType> (0.05 / 0.0259)) - static_cast<FloatType> (1.0));
+}
+} // namespace ame

test/test.cpp

@@ -9,6 +9,20 @@
 
 using doctest::Approx;
 
+TEST_CASE ("Circuit modeling")
+{
+ SUBCASE ("Diode")
+ {
+ CHECK_GT (ame::diode (1.0f), 1.0);
+ CHECK_EQ (ame::diode (0.5f), Approx (0.325089f));
+ CHECK_EQ (ame::diode (0.1f), Approx (0.042589f));
+ CHECK_EQ (ame::diode (0.0f), Approx (0.0f));
+ CHECK_EQ (ame::diode (-0.25f), Approx (-0.076568f));
+ CHECK_EQ (ame::diode (-0.8f), Approx (-0.157312f));
+ CHECK_GT (0.0f, ame::diode (-1.0f));
+ }
+}
+
 TEST_CASE ("Radian / Degree")
 {
  CHECK_EQ (ame::rad2deg (0.0f), Approx (0.0f));