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COMPONENTES ELECTRONICOS Practica de Sistemas Electronicos Practica de diodos Practica de transistores
Practica de Amplificador Practica de Realimentacion Practica con Operacional  

 

 

 

Enunciado de la Practica

Calculo teorico del amplificador multietapa, Av, fl, fh, Zi, Zo

  • Frecuencias medias

    La primera etapa es un amplificador emisor comun.


    \begin{displaymath}\beta=290\end{displaymath}


    \begin{displaymath}r_{\pi_{1}}=\frac{V_{T}}{I_{B_{1}}}=\frac{26\,10^{-3}}{19.61\,10^{-6}}=1325.85\,\Omega\end{displaymath}


    \begin{displaymath}R_{i_{1}}=R_{1}\vert\vert R_{2}\vert\vert(r_{\pi})=1309\,\Omega\end{displaymath}




    \begin{displaymath}R'_{L}=R_{i_{2}}\vert\vert R_{C_{1}}\end{displaymath}




    \begin{displaymath}R_{o}=R_{C_{1}}=1\,k\Omega\end{displaymath}




    \begin{displaymath}A_{v_{1}}=-\frac{\beta \,R'_{L_{1}}}{r_{\pi}+0}\end{displaymath}




    La segunda etapa es un amplificador seguidor de emisor.


    \begin{displaymath}\beta=190\end{displaymath}


    \begin{displaymath}r_{\pi_{2}}=\frac{V_{T}}{I_{B_{1}}}=\frac{26\,10^3}{6.66\,10^{-6}}=3903.9\,\Omega\end{displaymath}


    \begin{displaymath}A_{v_{2}}=\frac{(\beta+1)\,R'_{L_{2}}}{r_{\pi}+(\beta+1)\,R'_{L_{2}}}=0.99\end{displaymath}


    \begin{displaymath}R'_{L_{2}}=R_{E_{2}}\vert\vert R_{L_{2}}=R_{E_{2}}=3.3\,k\Omega\end{displaymath}




    \begin{displaymath}R_{o_{2}}=R_{E_{2}}\vert\vert\frac{r_{\pi}+R'_{S_{2}}}{\beta+...
...0^3\vert\vert 330\,10^3\vert\vert 330\,10^3}{191}=25.45\,\Omega\end{displaymath}


    \begin{displaymath}R_{i_{2}}=R_{B}\vert\vert(r_{\pi}+(\beta+1)\,R'_{L_{2}})=130.78\,k\Omega\end{displaymath}





    \begin{displaymath}R'_{L_{1}}=130.78\,10^3\vert\vert 1\,10^3=992.41\,\Omega\end{displaymath}




    \begin{displaymath}A_{v_{1}}=\frac{\beta\,R'_{L_{1}}}{r_{\pi}+0}=\frac{290\cdot 992.41}{1325.85+0}=217.15\end{displaymath}





    \begin{displaymath}A_{v}=A_{v_{1}}\,A_{v_{2}}=-214.97\end{displaymath}


    \begin{displaymath}R_{i}=1309\,\Omega\end{displaymath}


    \begin{displaymath}R_{0}=25.45\,\Omega\end{displaymath}





  • Frecuencias bajas

    \begin{displaymath}f_{L_{1}}=\frac{1}{2\,\pi\,(R_{i}+R_{s})\,C_{1}}=\frac{1}{2\cdot\pi\cdot (1309+50)\cdot 100\,10^{-9}}=1.17\,kHz\end{displaymath}


    \begin{displaymath}f_{L_{2}}=\frac{1}{2\,\pi\,(R_{o_{1}+R_{i_{2}}})\,C_{2}}=\fra...
...{2\cdot\pi\cdot(1\,10^3+130.78\,10^3)\cdot 100\,10^{-9}}=12\,Hz\end{displaymath}


    \begin{displaymath}f_{L_{3}}=\frac{1}{2\,\pi\,R'_{E_{1}}\,C_{E}}=\frac{1}{2\,\pi...
...ert\vert 150\,10^3\vert\vert 50}{291}))\,4.7\,10^{-6}}=7.3\,kHz\end{displaymath}





    \begin{displaymath}f_{L}=7.3\,kHz\end{displaymath}





  • Frecuencias altas


    \begin{displaymath}f_{T}=100\,MHz\end{displaymath}


    \begin{displaymath}C_{\mu_{1}}=1.5\,pF\end{displaymath}


    \begin{displaymath}C_{\pi_{1}}=\frac{\beta_{1}}{2\,\pi\,r_{\pi_{1}}\,f_{T_{1}}}-...
...{1}}=\frac{290}{2\,\pi\,1325.85\,100\,10^{6}}-C_{\mu}=346.6\,pF\end{displaymath}




    \begin{displaymath}R'_{S_{1}}=r_{\pi_{1}}\vert\vert(r_{x_{1}}+(R_{1}\vert\vert R...
...(0+(330\,10^3\vert\vert 150\,10^3\vert\vert 50))=48.16\,\Omega \end{displaymath}


    \begin{displaymath}R'_{L_{1}}=R_{i_{2}}\vert\vert R_{L_{1}}=130.78\,10^3\vert\vert 1\,10^3=992.41\,\Omega\end{displaymath}


    \begin{displaymath}g_{m_{1}}=\frac{\beta}{r_{\pi}}=\frac{290}{1325.85}=0.22\end{displaymath}


    \begin{displaymath}C_{T_{1}}=C_{\pi}+C_{\mu}\,(1+g_{m}\,R'_{L})=346.6\,10^{-12}+328\,10^{-12}=675.2\,pF\end{displaymath}


    \begin{displaymath}f_{H_{1}}=\frac{1}{2\,\pi\,R'_{S}\,C_{T}}=4.89\,MHz\end{displaymath}





    \begin{displaymath}f_{T}=250\,MHz\end{displaymath}


    \begin{displaymath}C_{\mu_{1}}=4.5\,pF\end{displaymath}


    \begin{displaymath}C_{\pi_{2}}=\frac{\beta_{1}}{2\,\pi\,r_{\pi_{2}}\,f_{T_{2}}}-...
..._{2}}=\frac{190}{2\,\pi\,3903.9\,250\,10^{6}}-C_{\mu}=26.48\,pF\end{displaymath}




    \begin{displaymath}R'_{S_{2}}=(r_{x_{2}}+(R_{3}\vert\vert R_{4}\vert\vert R_{o_{1}}))=(0+(330\,10^3\vert\vert 330\,10^3\vert\vert 1\,10^3))=993.97\end{displaymath}


    \begin{displaymath}R'_{L_{2}}=R_{E_{2}}\vert\vert R_{L_{2}}=3.3\,k\Omega\end{displaymath}


    \begin{displaymath}g_{m_{2}}=\frac{\beta}{r_{\pi}}=\frac{190}{3903.9}=0.05\end{displaymath}


    \begin{displaymath}C_{T_{2}}=C_{\mu}+\frac{C_{\pi}}{1+g_{m}\,R'_{L}}=4.5\,10^{-12}+\frac{26.48\,10^{-12}}{1+0.05\cdot 3.3\,10^3}=4.65\,pF\end{displaymath}


    \begin{displaymath}R_{T_{2}}=R'_{S}\vert\vert(r_{\pi}+(1+g_{m}\,R'_{L}))=993.97\vert\vert(3903.8+(1+0.05\cdot 3.3\,10^3))=798.86\,\Omega\end{displaymath}


    \begin{displaymath}f_{H_{2}}=\frac{1}{2\,\pi\,R'_{T}\,C_{T}}=\frac{1}{2\cdot \pi\cdot 798.86\cdot 4.65\,pF}=42.78\,MHz\end{displaymath}


    \begin{displaymath}f_{H}=4.89\,MHz\end{displaymath}

cajael