Modeling the input non-quasi-static effect in small signal equivalent circuit based on charge partitioning for bipolar transistors and its impact on RF noise modeling

Graded Applications of NQS Theory for Modeling Correlated Noise in SiGe HBTs

“…Although one is free to choose a very accurate NQS model and highly approximated expressions for y-parameters while implementing the noise model, it is logical to have consistency in both. Our four-node model of (13) preserves this consistency since the y-parameters of (3) and (4) are used in (1) to obtain (7), implementation of which takes the form of (13). On the other hand, our single-node model of (15) uses highly approximated expressions of y-parameters that read which yields (8) [6] from (1) assuming A Q3 = 1 along with λ = 1.…”

“…it and ibei are the quasi-static transfer current and internal base current, respectively. Tf, kc, and alqf (3,4,5) correspond to τ f , k c , and A Q (3,4,5) , respectively. (14) can further be simplified by taking: 1) A Q = 0 in all the denominator terms; 2) A Q5 = 0; and 3) A Q4 = 0, which convert (14) into…”

“…In [2], one can find an account of the various noise PSDs corresponding to the different noise models of BJTs. It also attempts to develop an implementationsuitable correlated noise model based on [3] and [4]. However, the simplified model of [2] does not use the same set of model parameters used in the underlying NQS model.…”

Modeling high-frequency noise in SiGe HBTs using delayed minority charge

“…Since in forward active operation, effects of y 12 and y 22 are negligible in (2), we did not consider them in formulating our model. First of all, this assumption leads to [11], we observe that small-signal forward diffusion charge ΔQ f affects y 11 as well as y 21 ; hence, effectively determines input as well as the cross-correlated PSD terms of (2). Introducing a delay into the small-signal QS forward diffusion charge ΔQ f0 (=g m0 τ f Δv B ), we obtain (with τ f as transit time and A Q as model parameter)…”

“…The delayed minority charge (3) suffices to model the y 11 and y 21 , except the phase of the latter [1]. If a further extra phase to be incorporated in (y 21 (ω)-g m0 ) equals exp(-jωτ D0 ) (with τ D0 as model parameter), …”