Matlab (Student Version) Matlab control file - go.m data12ax7.m coeff.m interp.m final.m Matlab Results (stored coefficients)
Pspice files (used with Intusoft Demo Version 5.0/6.0)
I like Koren's effort a lot because it uses some interesting functions to accomplish tube-like "transfer" trends ... except that it doesn't mimic the curvature of tube very well in areas of standard operation, and the use of a diode to model the input circuit has been questioned by some ... his model certainly has great converging properties which can happen if strictly monotonic functions are used throughout (as composite functions) ... Koren's method is based on the insistance that, according to classic theory, the plate current characteristics are well approximated by the standard 3/2 power expression ... the model I stumbled on is based on polynomial functions which are generated using "sampled" data points (RCA's and GE's in this case) ... all that is required to show is how (qualitatively and not just quantitatively) (i)a) data is well approximated on the sampled data and (i)b) on the curves they are taken from and (ii) to assure that there's a strong sense of continuity in how transfer curvature evolves in between the mutual characteristic curves (data) ... since small-signal simulations depend on modeling accuracy in the first order derivative on the data, it follows that strong "slope" accuracy is required of the models ... for example, if a device model generates a copy of a data curve that initially starts off a little low in comparison with data and then it ends a little higher against it then there's a good chance that where the two curves cross there will be different crossing slopes near and on that point ... this means that small-signal parameters, which are usually taken in and arond the weak spots of Koren's model, are likely to be off by a considerable amount as a result ... plotting the Koren model against RCA triode data shows that the modeling is not very good even in an absolute sense, but still it could be possible to produce a model that exhibits good absolute error but poor slope error ... In this approach I've tested out the modeling can produce micro oscillations around a data curve simply by choosing interpolation "order" to a too high degree (versus the number of data points given ... I don't mean to knock Mr. Koren's efforts, in comparison my models might have a very hard time converging in circuits that his models would glide through ... the reason for this is the dual-nature of my models, both plate and grid ports are modeled by bi-variable non-linear polynomial functions which may start fighting with one another if initial conditions are not set properly at the onset of a simulation ... even though this new model is to be taken as experimental I have a feeling that high accuracy levels can be reached using a generalized approach ... the Completeness Theorem in the Space of Real valued Functions (in regards to polynomial function spaces) certainly adds support to using this kind of approach ...
Model comparison between Koren's and Mine Common Cathode Transfer Sim *with older GE model Non-linear Cascaded Circuit Sim
~:( HOME :)~
viva Analog /// jc -> lynx.net