ZamTube: Use thevenin equivalent for tube as a voltage generator + variable resistorzamtube-optimise

1 files changed, 39 insertions, 9 deletions

diff --git a/plugins/ZamTube/triode.cpp b/plugins/ZamTube/triode.cpp
index ac5ff6e..d48f097 100644
--- a/plugins/ZamTube/triode.cpp
+++ b/plugins/ZamTube/triode.cpp
@@ -5,7 +5,8 @@
 using std::abs;
 #define DUMP(x) x
 
-T Triode::compute(T a, T R, T Vg, T Vk) {
+#if 0
+T Triode::compute_old(T a, T R, T Vg, T Vk) {
 	T VakGuess = 100.;
 	T Vgk = Vg - Vk;
 	T Vak = VakGuess;
@@ -22,6 +23,7 @@ T Triode::compute(T a, T R, T Vg, T Vk) {
 	//printf("Vgate=%f Vk=%f  Vgk=%f b=%f\n", Vgate, Vk, Vgk, b);
 	return b;
 }
+#endif
 
 T Triode::getIa(T Vgk, T Vpk) const {
 	if (Vpk < 0.0) {
@@ -47,16 +49,43 @@ T Triode::iterateNewtonRaphson(T x, T dx, T Vgk, T a, T R) const {
 	return xNew;
 }
 
+
+T Triode::compute(T a, T R, T Vg, T Vk) {
+	T mu1, vp2, vgg, evgg, evgg1, levgg1, powkx, pkxvg;
+	T dIpVp, ra;
+	T Vp, Ip, Vpk, Vgk, b;
+
+	Vgk = Vk - Vg;
+	Vpk = -mu * Vgk;
+	Ip = getIa(Vgk, Vpk);
+
+	b = Vpk - R*Ip;
+	Vp = a - R*Ip;
+
+	mu1 = 1.0/mu;
+	vp2 = sqrt(Vp*Vp + kvb);
+	vgg = Vg / vp2 + mu1;
+	evgg = exp(kp*vgg);
+	evgg1 = 1. + evgg;
+	levgg1 = log1p(evgg);
+	powkx = pow(Vp*levgg1/kp, kx - 1.0);
+	pkxvg = kx*powkx*evgg;
+
+	dIpVp = pkxvg/(vp2*evgg1);
+	ra = kg1 / dIpVp;
+	if (ra < 1.)
+		ra = 1.;
+	
+	//dIpVg = Vp*pkxvg*(vgg/(kp*evgg1) - levgg1/(kp*kp));
+	//gm = dIpVg / kg1;
+	
+	b = Vpk - (R + 0.1/ra)*Ip;
+	return b;
+
+}
+
 Triode::Triode()
 {
-	/* good for low gain, broken at high gain
-	kvb = 300.;
-	mu = 103.2;
-	kx = 1.26;
-	kg1 = 446.0;
-	kp = 3.4;
-	*/
-	
 	//12AX7 RSD-1 (custom)
 	mu = 100.;
 	kx = 1.4;
@@ -64,3 +93,4 @@ Triode::Triode()
 	kp = 600.;
 	kvb = 300.;
 }
+