Dear QUCS team,

first of all, congratulations and my very respect for
your ambitious project! I particularly like the concise compilation of all the
models and the math behind SPICE, you are providing.

Since I’m currently dealing with BJT noise (in
a very low noise TIA application), I had a closer look at the BJT noise model
(fig. 10.15) and related equations. The noise sources ib^2 and ic^2 from equations
10.145 and 10.146 are very clear to me, but how do the contributions of the
ohmic resistances Rbb, Rc, Re (equ. 10.144) fit into the figure 10.15 noise
model ? None of the terms shows up there, but at least Rbb can not be neglected
for a decent noise calculation.

To my knowledge the noise contribution of Rbb can be regarded
as voltage source with ubb^2 = 4KTRbb and placed in series with Rbb of figure
10.10. But what about the noise contributions of Rc and Re – convert them
into voltage sources and place them in series with Rc and Re of the figure
10.10 model as well ? However, it’s not quite clear from this
document, what the simulator actually calculates….

So could you please enhance the fig. 10.15 noise
model with the Rbb, Rc, Re noise sources – or let me know what I
overlooked !

(btw.: the very similar questions arise regarding the
FET- and Diode- noise models.)

Best regards,

Markus Mettenleiter

(R&D engineer)