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這是小弟寫的文章 編講義用的 歡迎高手同行找碴:
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This section highlights the importance of an accurate pre-determined DC compact model.\cite{dc!!!}
- M. A6 I6 K! f, B$ B0 NFor compact model developers, extraction of the DC parameters always needs to be carried out before the extraction of AC ones.
5 k* S$ J! I! z2 Z% q+ nFor devices measurement, DC measurement has to be carried out before AC measurement.
; X' m8 b9 |" G- C6 Z4 m8 d9 ZFor modern IC designers, DC analysis needs to be carried out before AC analysis.\cite[4.6.4]{smith!}0 j: M3 S1 V" x- F, Z$ O3 G
For SPICE-like simulators, DC simulation also needs to be swept first and then follows by AC simulation.\cite{nlz!}
: I3 h h, g7 GFrom the device-level perspectives,
/ d# Q+ V5 \+ q' I' Xa set of equations which describe the terminal characteristics of DUT are written in a compact model.
8 o8 ?; X* p2 j. P% N- u1 O1 g4 EThe equations are solved by SPICE-like simulators." b1 U* U7 F3 p4 Z6 T
The procedure of establishing equations, describing device's electrical characteristics, in a compact model
/ {0 }5 h7 z: v, P: ~4 ~2 ~8 wand have them solved by SPICE-like simulators is termed as: Device Characterization.
2 o1 S1 @6 c# BThe fully Characterizations are treated by two independent steps:
7 Z j/ }$ w+ h. `8 }% s, ](1)DC Characterization or DC parameters extraction
* X' |7 x# I" ]& q(2)AC Characterization or AC parameters extraction
& O2 C7 |% H/ V# m0 tCharacterizing a nonlinear electronics component always begins with
3 f, K& l) v2 I8 Q( N$ U3 hDC characterization and follows by the AC characterization.9 Z1 E# ?! d0 v$ v( U- }2 C. B
Because the AC model is origined from the linearization of the DC model at an indicated operating point.0 k3 Q' r9 ^- y$ l9 \
Accordingly, accuracy is highly required in DC characterization because of its piority in the procedure of parameter extraction .
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From the circuit-level perspectives,,2 T+ W/ X7 e' P$ b
Circuit analysis refers to solving a circuit with KVL and KCL.
. D& Q) ~ _' n4 R+ LTo be more specific, it means solving out nodes voltages and branches currents of each element in a circuit.8 E2 Y T! z2 @- K( r
As the source of stimulus can be systematically separated into DC sources and AC sources,2 _% d* @+ w" l
the unknown/solutions of the circuit are also separated into DC part and AC part.
/ K& g1 v8 T3 ?1 u) cAnalyzing a circuit is treated in two independent meansA)DC analysis (B)AC analysis
' U# \' {# Z' a( T: G( u, xThe separation between DC analysis and AC analysis greatly simplified a complex circuit.' {$ |- A1 p9 v- X2 X7 k
DC analysis is being carried out before AC analysis.
+ n. C- {2 Z* P) uDC analysis determines the Q-point, including each node voltage and branch current.) X2 h) [7 H4 Z& A0 X+ e; Z+ W
AC analysis gives the frequency response, including bandwidth and gain.; t. W/ W0 N' z2 U
Before performing AC Analysis, the DC operating point needed to be calculated from DC analysis first.$ I1 O* c9 m: ~5 |
This is to construct a linear small-signal model for the nonlinear component.
; G, Q! C- l' y* X" sSo, the small signal (AC) response is highly dependent upon the presetting (DC) bias condition .
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2 |6 M% d: z X) \DC simulation in analog SPICE-like simulator, aims for computing the equilibrium points,- {- h% W2 O. @. n2 h& \
which are the calculated DC node voltages and DC branch currents in a circuit.; z# ~$ u i+ ~4 Q5 L0 w# B% C) l
They are the DC solutions of the DC equivalent equation/circuit.
7 S- c( @. x0 |1 R5 O0 GA circuit will only reach its equilibrium if its stimulus is off
/ S1 `# R j# }9 a% R$ eand the independent sources are remain constantly employed.4 p1 \) `4 E8 C
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There is an important reason why a given electronics circuit always
3 S6 E6 P9 I0 p: qneed to be reduced into a DC equivalent circuit (large-signal model)
' r! B' B8 R% Q0 O. Kand followed by an AC equivalent one(small-signal model).
' u6 v1 Y0 h2 v4 X4 T7 @It has to do with the present of an active component in the circuit.
( O4 V* L) f* g' H M5 h% u" lThe active component is a nonlinear element.So, it will have to be linearized.4 Q m% k' N& T; t( b% b# C
The employment of active elements, like transistors, make the circuit a nonlinear algebra system.
$ E- O" u1 y! ~4 ^, u8 d3 T O3 ENormally, the nonlinear equation can only be solved by means of iterative methods,
. c5 q3 V. f A5 p2 _# ksuch as Newton-Raphson algorithm \cite{nlz!}. This algorithm transforms the solutions
' A4 E5 ]. m4 k' h' {6 U0 z# U4 A8 iof the nonlinear equation into a sequence of linear equation.7 q% C! L/ u w7 [( H% \
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