From: Antonio <tritemio@gm...>  20060622 07:47:16

Hi to the list, having understood how to simulate the noise in ac I've patched another simple example with BJT and flicker noise. It is very nice to see the correspondence between the simulated values and those synthetically calculated "by hand". The sch and dpl files are attached. Maybe it's a good example to be added to the download section, but first I want to refine it a bit more. I saw the function.pdf file published the past month, and I discovered that I can refer to any component parameter using the syntax ComponentName.Parameter. Unfortunately if I try to insert in an equation the R2 value (using R2.R) or the BTJ betha forward value (Q1.Bf) I get an error during the simulation saying: checker error, undefined variable `Q1.Bf' in equation `Rpi' Most probably I'm again missing something very trivial here. Any hint? Another question I have about the circuit is the temperature dependence. I have assumed that the Temp parameter in the BJT properties is the junction Temperature. So 25=B0 is not a realistic value, 100=B0 seems to me a more realistic one. If I increase the Temp value, the noise increase correspondingly. Giving that the noise is dominated by the base noise current (the white component is [2 e Ib]) I wonder which is the BJT parameter variation that cause the noise to increase. In fact, at first glance, both the base current and the trans conductance are constant, so even the noise should remain constant, isn't it? I'll will investigate more deeply on this point... The last question, is a bit tangential. Which is the best way to simulate the trans conductance value (gm) accurately? Theoretically I can apply a small sinusoidal voltage source to the base and calculate the signal current, but is there an "non invasive" way to calculate this parameter?. Many Thanks. Cheers, ~ Antonio 