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+// Example 10.19: Approximate value of fH
+clc, clear
+btaf=150;
+VA=120; // in volts
+fT=400e6; // in hertz
+C_mu=0.5e-12; // in farads
+ICQ=100e-6; // in amperes
+RS=50e3; // in ohms
+RC=250e3; // in ohms
+VT=25e-3; // Voltage equivalent to temperatue at room temperature in volts
+gm=ICQ/VT; // in mho
+r_pi=btaf/gm;  // in ohms
+ro=VA/ICQ; // in ohms
+C_pi=btaf/(2*%pi*fT*r_pi)-C_mu; // in farads
+function[c]=parallel(a,b)
+    c=a*b/(a+b);
+endfunction
+// From AC model in Fig. 10.73
+Ri=r_pi+(1+btaf)*parallel(ro,r_pi); // in ohms
+R_mu1=parallel(RS,Ri); // in ohms
+// From Fig. 10.75(b)
+R=(50+36.36)/(1+145); // in ohms
+R_pi1=parallel(r_pi,R); // in ohms
+R_pi2=parallel(r_pi,parallel((RS+r_pi)/(1+btaf),ro)); // in ohms
+RL=parallel(ro,RC); // in ohms
+R_mu2=R_pi2*(1+gm*RL)+RL; // in ohms
+a1=R_mu1*C_mu+R_pi1*C_pi+R_pi2*C_pi+R_mu2*C_mu; // in seconds
+fH=1/(2*%pi*a1); // in hertz
+fH=fH*1e-3; // in kilo-hertz
+disp(fH,"Approximate value of fH (kHz) =");
+\ No newline at end of file