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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) const {
if (Vpk < 0.0) {
Vpk = 0.0;
}
if (Vgk > 0.0) {
Vgk = 0.0;
}
/* f(x,y) = (y*log(1+kp/mu*exp(1+mu*x/sqrt(kvb+y*y))))^kx
* = (y*log(1+6*exp(1+100*x/sqrt(300+y*y))))^1.4
*
* Let y' = y * sqrt(300)
* Let x' = x * 100 / sqrt(300)
*
* f(x',y') = (y'*log(1+6*exp(1+x'/sqrt(1+y'*y'))))^1.4
*
* When -x'/y' < 17
* f(x',y') ~= (y' - 3*exp(1)*x')^1.4
* f(x,y) ~= (y/sqrt(300) - 3*exp(1)*x*sqrt(300)/100)^1.4
*
* When |x'| is small && y' is large
* f(x',y') ~= (y'*log(1 + 6*exp(1)))^1.4
* f(x,y) ~=(y/sqrt(300)*log(1 + 6*exp(1)))^1.4
*
* Otherwise, use exact solution
*/
float f = 0.f;
float sc = 1e+6 / kg1;
/*
#define G_NEG_SMALL -1.f
#define P_LARGE 150.f
float e1 = expf(1.f);
float r300 = sqrtf(300.f);
if (-Vgk/Vpk < 17.) {
f = sc * powf(Vpk / r300 - 3.f * e1 * Vgk * r300 / 100., 1.4f);
} else if ((Vgk > G_NEG_SMALL) && (Vpk > P_LARGE)) {
f = sc * powf(Vpk * log1pf(6.f*e1) / r300, 1.4f);
} else {
*/
/* exact solution (expensive) */
float ee1 = Vpk*log1pf(expf(kp*(1./mu+Vgk/sqrtf(kvb+Vpk*Vpk))))/kp;
if (ee1 < 0) {
return 0.;
}
f = sc * powf(ee1, kx);
// }
//printf("Vpk=%f e1=%f exact_e1=%f\n", Vpk, ans, e1, ee1);
return f;
}
T Triode::iterateNewtonRaphson(T x, T dx, T Vgk, T a, T R) const {
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()
{
/* 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;
kg1 = 446.;
kp = 600.;
kvb = 300.;
}
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