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A. 等価回路

A..1 電圧源モデル

等価回路は,図19のようになります.
図 19: 電圧源モデルによるSRPPの等価回路
\begin{figure}\input{figs/srpp_eqv}
\end{figure}

等価回路より,以下の関係が成り立ちます.

μ1(ei - i1Rk1) = i1(rp1 + Rk1 + Rk2) + (i1 - i2)RL (54)
μ2eg2 = (i2 - i1)RL + i2rp2 (55)
eg2 = - i1Rk2 (56)
eo = (i2 - i1)RL (57)

式(56)を 式(55)に代入して,
- μ2i1Rk2 = (i2 - i1)RL + i2rp2  
(- μ2Rk2 + RL)i1 = (RL + rp2)i2 (58)

式(54)を整理して,

μ1ei = {rp1 + (μ1 +1)Rk1 + Rk2 + RL}i1 - RLi2 (59)
式(57)より,
eo = RLi2 - RLi1  
i2 = $\displaystyle {\frac{{e_o + R_L i_1}}{{R_L}}}$ = $\displaystyle {\frac{{e_o}}{{R_L}}}$ + i1 (60)

式(60)を 式(58)に代入して,
(- μ2Rk2 + RL)i1 = (RL + rp2)($\displaystyle {\frac{{e_o}}{{R_L}}}$ + i1)  
(- μ2Rk2 - rp2)i1 = eo$\displaystyle {\frac{{R_L+r_{p2}}}{{R_L}}}$  
i1 = - $\displaystyle {\frac{{r_{p2}+R_L}}{{(r_{p2}+\micro_2 R_{k2})R_L}}}$eo (61)

式(60)を 式(59)に代入して,
μ1ei = {rp1 + (μ1 +1)Rk1 + Rk2 + RL}i1 - RL($\displaystyle {\frac{{e_o}}{{R_L}}}$ + i1)  
μ1ei + eo = {rp1 + (μ1 +1)Rk1 + Rk2}i1  

式(61)より,
μ1ei + eo = - $\displaystyle {\frac{{\{r_{p1}+(\micro_1+1)R_{k1}+R_{k2}\}(r_{p2}+R_L)}}{{(r_{p2}+\micro_2 R_{k2})R_L}}}$eo  
- μ1ei = $\displaystyle {\frac{{\{r_{p1}+(\micro_1+1)R_{k1}+R_{k2}\}(r_{p2}+R_L)+(r_{p2}+\micro_2 R_{k2})R_L}}{{(r_{p2}+\micro_2 R_{k2})R_L}}}$eo  
eo = - μ1ei$\displaystyle {\frac{{(r_{p2}+\micro_2 R_{k2})R_L}}{{\{r_{p1}+(\micro_1+1)R_{k1}+R_{k2}\}(r_{p2}+R_L)+(r_{p2}+\micro_2 R_{k2})R_L}}}$  
  = - μ1ei$\displaystyle {\frac{{(1+\frac{\micro_2}{r_{p2}}R_{k2})R_L}}{{\{r_{p1}+(\micro_...
..._{k1}+R_{k2}\}\frac{r_{p2}+R_L}{r_{p2}}+(1+\frac{\micro_2}{r_{p2}}R_{k2})R_L}}}$  
  = - μ1ei$\displaystyle {\frac{{(1+g_{m2}R_{k2})R_L}}{{\{r_{p1}+(\micro_1+1)R_{k1}+R_{k2}\}\frac{r_{p2}+R_L}{r_{p2}}+(1+g_{m2}R_{k2})R_L}}}$  
  = - μ1ei$\displaystyle {\frac{{R_L}}{{\frac{r_{p1}+(\micro_1+1)R_{k1}+R_{k2}}{1+g_{m2}R_{k2}}\cdot\frac{r_{p2}+R_L}{r_{p2}}+R_L}}}$  
  = - μ1ei$\displaystyle {\frac{{\frac{r_{p2}R_L}{r_{p2}+R_L}}}{{\frac{r_{p1}+(\micro_1+1)R_{k1}+R_{k2}}{1+g_{m2}R_{k2}}+\frac{r_{p2}R_L}{r_{p2}+R_L}}}}$  
  = - μ1ei$\displaystyle {\frac{{r_{p2}//R_L}}{{\frac{r_{p1}+(\micro_1+1)R_{k1}+R_{k2}}{1+g_{m2}R_{k2}}+r_{p2}//R_L}}}$  

したがって,ゲイン A は,

A = - μ1$\displaystyle {\frac{{r_{p2}//R_L}}{{\frac{r_{p1}+(\micro_1+1)R_{k1}+R_{k2}}{1+g_{m2}R_{k2}}+r_{p2}//R_L}}}$ (62)

A..2 電流源モデル

等価回路は,図20のようになります.
図 20: 電流源モデルによるSRPPの等価回路
\begin{figure}\input{figs/srpp_eqi}
\end{figure}

等価回路より,以下の関係が成り立ちます.

eg1 = ei - i1Rk1 (63)
eg2 = - i1Rk2 (64)
eo = (i2 - i1)RL (65)
i1Rk1 = ep1 + eg2 + eo (66)
i1 = gm1eg1 - $\displaystyle {\frac{{e_{p1}}}{{r_{p1}}}}$ (67)
i2 = gm2eg2 - $\displaystyle {\frac{{e_o}}{{r_{p2}}}}$ (68)

式(64)を式(66)に代入して,
i1Rk1 = ep1 - i1Rk2 + eo  
ep1 = (Rk1 + Rk2)i1 - eo (69)

式(63), (69)を式(67)に代入して,
i1 = gm1(ei - i1Rk1) - $\displaystyle {\frac{{e_{p1}}}{{r_{p1}}}}$  
  = gm1(ei - i1Rk1) - $\displaystyle {\frac{{(R_{k1}+R_{k2})i_1-e_o}}{{r_{p1}}}}$  
(1 + gm1Rk1 + $\displaystyle {\frac{{R_{k1}+R_{k2}}}{{r_{p1}}}}$)i1 = gm1ei + $\displaystyle {\frac{{e_o}}{{r_{p1}}}}$  
{(1 + gm1Rk1)rp1 + Rk1 + Rk2}i1 = gm1rp1ei + eo  
(rp1 + μ1Rk1 + Rk1 + Rk2)i1 = μ1ei + eo  
i1 = $\displaystyle {\frac{{\micro_1 e_i + e_o}}{{r_{p1} + (\micro_1+1)R_{k1}+R_{k2}}}}$ (70)

式(64)を式(68)に代入して,
i2 = - gm2i1Rk2 - $\displaystyle {\frac{{e_o}}{{r_{p2}}}}$ (71)

式(71)を式(65)に代入して,
eo = (- gm2i1Rk2 - $\displaystyle {\frac{{e_o}}{{r_{p2}}}}$ - i1)RL  
  = - (1 + gm2Rk2)RLi1 - $\displaystyle {\frac{{R_L}}{{r_{p2}}}}$eo (72)

式(70)を代入して,
eo = - $\displaystyle {\frac{{(1 + g_{m2}R_{k2})R_L(\micro_1 e_i + e_o)}}{{r_{p1}+(\micro_1+1)R_{k1}+R_{k2}}}}$ - $\displaystyle {\frac{{R_L}}{{r_{p2}}}}$eo  
(1 + $\displaystyle {\frac{{R_L}}{{r_{p2}}}}$ + $\displaystyle {\frac{{(1+g_{m2}R_{k2})R_L}}{{r_{p1}+(\micro_1+1)R_{k1}+R_{k2}}}}$)eo = - μ1ei$\displaystyle {\frac{{(1+g_{m2}R_{k2})R_L}}{{r_{p1}+(\micro_1+1)R_{k1}+R_{k2}}}}$  
eo = - μ1ei$\displaystyle {\frac{{\frac{(1+g_{m2}R_{k2})R_L}{r_{p1}+(\micro_1+1)R_{k1}+R_{k...
...{R_L}{r_{p2}} + \frac{(1+g_{m2}R_{k2})R_L}{r_{p1}+(\micro_1+1)R_{k1}+R_{k2}}}}}$  
  = - μ1ei$\displaystyle {\frac{{R_L}}{{\frac{r_{p2}+R_L}{r_{p2}}\cdot\frac{r_{p1}+(\micro_1+1)R_{k1}+R_{k2}}{1+g_{m2}R_{k2}} + R_L}}}$  
  = - μ1ei$\displaystyle {\frac{{\frac{r_{p2}R_L}{r_{p2}+R_L}}}{{\frac{r_{p1}+(\micro_1+1)R_{k1}+R_{k2}}{1+g_{m2}R_{k2}}+\frac{r_{p2}R_L}{r_{p2}+R_L}}}}$  
  = - μ1ei$\displaystyle {\frac{{r_{p2}//R_L}}{{\frac{r_{p1}+(\micro_1+1)R_{k1}+R_{k2}}{1+g_{m2}R_{k2}}+r_{p2}//R_L}}}$  

したがって,ゲイン A は,

A = - μ1$\displaystyle {\frac{{r_{p2}//R_L}}{{\frac{r_{p1}+(\micro_1+1)R_{k1}+R_{k2}}{1+g_{m2}R_{k2}}+r_{p2}//R_L}}}$ (73)


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Next: この文書について... Up: 作図で理解するSRPP Previous: 8 まとめ

平成16年5月14日