Electric Circuits 8th Edition 146

Electric Circuits 8th Edition 146 - the circuit shor\n in...

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122 Techniques of Circuit Anatysis Find the Th6venin equivalent for the circuit con taining dependent sources shown in Fig- '1.49. Figure 4.49 a A circuit us€d to itLustraie a Th6venin eqLrilatent when the circuit contajns dependent sources. Sotution The first slep i]l analyzing the circuit in Fig 4'19 js to recognize that the current labcled i. must be zero. (Note the abscnce of a retum path for ir to enter the leffhand portion of the cjrcuit.) The open circuit, or Th6venin. voltage will be the voll age across the 25 O rcsistor.With i" : {), Yrh=oob:( 20t(2s) = 500i' The current i is 5-30 5 3yft ': 2ooo : ,(no ' In writing t}le equation for i, wc recognize that the Th6venin voltage is identical to the control voltage wllen we combine these two equalions,we obtarl Yrh=-5v To calculate the short-circuit curent, we place
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Unformatted text preview: the circuit shor\n in Fig. 4.4,r becomer lhe one \ho$n in Fig. 4.50. WitI the sho.t circuit shunting the 25 O resistor. all the curent from the dependent cunent source appears in the short,so Finding the Thdvenin Equivalent of a Circuit with a Dependent Source Figure 4.50 s The circuit shown in Fig. 4.49 wiih termjnaLs a As the voltage controlling the dependent volt-age source has been reduced to zero, the current controlling the dependent current source is Combining these two equations yields a shortcircuit i," = 20(2s) = 50 mA. From i,. and Yrh we gel 5 2000 Figure 4.51 illustrates the Th6venin equivalent for the circuit shown in Fig.4.,19. Note that the ref erence polarity marks on the Th6venin voltage source in Fig. ,{.51 agree witb the preceding equa-tion for Yft.- x 10e = 100O. Figure 4.51',. The Th6venin equjvahntforihe cncuit shown in Fil.4.49. 100() (' 2ko...
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