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#include <stdio.h>
#include <inttypes.h>
#include <cmath>
#include "triode.h"
using std::abs;
#define DUMP(x) x
T Triode::compute(T a, T R, T Vg, T Vk) {
T VakGuess = 100.;
T Vgk = Vg - Vk;
T Vak = VakGuess;
int iteration = 0;
T err = 1e6;
for (iteration = 0; (fabs(err)/fabs(Vak) > EPSILON) && (iteration <= ITER); iteration++){
VakGuess = iterateNewtonRaphson(Vak, TOLERANCE, Vgk, a, R);
err = Vak - VakGuess;
Vak = VakGuess;
}
T b = Vak - R*getIa(Vgk, Vak);
//printf("Vgate=%f Vk=%f Vgk=%f b=%f\n", Vgate, Vk, Vgk, b);
return b;
}
T Triode::getIa(T Vgk, T Vpk) {
static bool prepared = false;
static double coeff[3];
if (!prepared) {
const double L2 = log(2.0);
const double scale = 1e+6*pow(L2, kx-2.0)/(8.0*pow(kp, kx));
coeff[0] = 8.0*L2*L2*scale;
coeff[1] = kx*kp*L2*4.0*scale;
coeff[2] = (kp*kp*kx*kx + L2*kp*kp*kx - kp*kp*kx) * scale;
prepared = true;
}
if (Vpk < 0.0) {
//printf("Less than zero!\n");
Vpk = 0.0;
}
if (Vgk > 0.0) {
Vgk = 0.0;
}
double A = 1./mu + Vgk / sqrt(kvb + Vpk*Vpk);
return Vpk*(coeff[0] + coeff[1]*A + coeff[2]*A*A) / kg1;
/* exact solution (takes > 3x longer)
e1 = Vpk*log1p(exp(kp*(1./mu+Vgk/sqrt(kvb+Vpk*Vpk))))/kp;
if (e1 < 0) {
return 0.;
}
return 1e+6*pow(e1, kx) / kg1;
*/
}
T Triode::iterateNewtonRaphson(T x, T dx, T Vgk, T a, T R){
T xIak = getIa(Vgk, x);
T dxIak = getIa(Vgk, x + dx);
T xNew = x - dx*(x + R*xIak - a)/(dx + R*(dxIak - xIak));
return xNew;
}
Triode::Triode()
{
//12AX7 RSD-1
kvb = 300.;
mu = 103.2;
kx = 1.26;
kg1 = 446.0;
kp = 3.4;
}
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