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+//chapter27
+//example27.4
+//page581
+
+hie=2000 // ohm
+hoe=1d-4 // mho
+hre=1d-3 
+hfe=50
+rL=600 // ohm
+
+Zin=hie-hre*hfe/(hoe+1/rL)
+// here second term can be neglected compared to hie so
+Zin_approx=hie
+
+Ai=hfe/(1+hoe*rL)
+// if hoe*rL << 1 then
+Ai_approx=hfe
+
+Av=-hfe/(Zin*(hoe+1/rL))
+// negative sign indicates phase shift between input and output
+
+printf("input impedence = %.3f ohm \n",Zin)
+printf("current gain = %.3f \n",Ai)
+printf("voltage gain = %.3f. Here negative sign indicates phase shift between input and output.\n \n",Av)
+
+printf("approximate input impedence = %.3f ohm \n",Zin_approx)
+printf("approximate current gain = %.3f \n",Ai_approx)