Question Solved1 Answer EXERCISES 8.4 If the op amp of Example 8.1 has a uniform -6-dB/octave high-frequency rolloff with 7 = 1 kHz. find the 3-dB frequency of the closed-loop gain V/V, Ans. 7 kHz 8.5 The circuit shown in Fig. E8.5 consists of a differential stage followed by an emitter follower, with series-shunt feedback supplied by the resistors R, and R. Assuming that the de component of V, is zero, and that B of the BJTs is very high, find the de operating current of each of the three transistors and show that the de voltage at the output is approximately zero. Then find the values of A. B. A = V/V, R. and Rout. Assume that the transistors have ß- 100. +10.7 V 20 ΚΩ 1Ο ΚΩ w R9K2 02 w OV. O SRI ΙΚΩ SMA -222 w I mA = RO Rout FIGURE E8.5 Ans. 85.7 V/V:0.1 V/V: 8.96 V/V: 191 k12: 19.1 92 R w A -OV V. + RL w R in lli RI w FIGURE E8.1 R w -OV V RL w R in lli w RI FIGURE E8.1

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Transcribed Image Text: EXERCISES 8.4 If the op amp of Example 8.1 has a uniform -6-dB/octave high-frequency rolloff with 7 = 1 kHz. find the 3-dB frequency of the closed-loop gain V/V, Ans. 7 kHz 8.5 The circuit shown in Fig. E8.5 consists of a differential stage followed by an emitter follower, with series-shunt feedback supplied by the resistors R, and R. Assuming that the de component of V, is zero, and that B of the BJTs is very high, find the de operating current of each of the three transistors and show that the de voltage at the output is approximately zero. Then find the values of A. B. A = V/V, R. and Rout. Assume that the transistors have ß- 100. +10.7 V 20 ΚΩ 1Ο ΚΩ w R9K2 02 w OV. O SRI ΙΚΩ SMA -222 w I mA = RO Rout FIGURE E8.5 Ans. 85.7 V/V:0.1 V/V: 8.96 V/V: 191 k12: 19.1 92 R w A -OV V. + RL w R in lli RI w FIGURE E8.1 R w -OV V RL w R in lli w RI FIGURE E8.1
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Transcribed Image Text: EXERCISES 8.4 If the op amp of Example 8.1 has a uniform -6-dB/octave high-frequency rolloff with 7 = 1 kHz. find the 3-dB frequency of the closed-loop gain V/V, Ans. 7 kHz 8.5 The circuit shown in Fig. E8.5 consists of a differential stage followed by an emitter follower, with series-shunt feedback supplied by the resistors R, and R. Assuming that the de component of V, is zero, and that B of the BJTs is very high, find the de operating current of each of the three transistors and show that the de voltage at the output is approximately zero. Then find the values of A. B. A = V/V, R. and Rout. Assume that the transistors have ß- 100. +10.7 V 20 ΚΩ 1Ο ΚΩ w R9K2 02 w OV. O SRI ΙΚΩ SMA -222 w I mA = RO Rout FIGURE E8.5 Ans. 85.7 V/V:0.1 V/V: 8.96 V/V: 191 k12: 19.1 92 R w A -OV V. + RL w R in lli RI w FIGURE E8.1 R w -OV V RL w R in lli w RI FIGURE E8.1
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Ans-8.4- From the Solution of Example 8.1,A beta=6So, quad1+A beta=7Thus, the 3-dB forequency of the closed-loop gain volvs is,{:[f_(Hf)=(1+AB)f_(H)],[f_(Hf)=7xx1],[f_(Hf)=7KHZ]:}Aw6-8.5- Refer to Fig, E8,5.The 1- MA bias Curent will split equally between the emitters of Q_(1) and Q_(2), thus,I_(E_(1))=I_(E_(2))=0.5mA". "Transistor Q_(3) will be operating at an emitter current, I_(E_(3))=5mA.determined ty the 5-mA Current Source, Since the dc component of v_(s)=0, the negative feedtack will force the dc voltage at the output to be approximately kero.The B Circuiet as Bhown in Fig.1 together with the determination of B and of the loading effect off the pcirlint on the Acircuit,{:[beta=(R_(1))/(R_(1)+R_(2))=(1)/(1+9)=0.1V//V],[R_(11)=R_(1)+1R_(2)=1119=0.9kOmega],[R_(22)=R_(1)+R_(2)=1+9=10kOmega]:}(3)The A ciorluit is shown in Fig.2,{:[r_(1)=re_(2)=(V_(T))/(I_(E_(1),2))=(25mV)/(0.5(mA))=50 Omega],[r_(3)=(V_(T))/(I_(E_(3)))=(25mV)/(5(mA))=5Omega]:}Now,{:[i_(e)=(V_(i))/(r_(e)+re_(2)+(R_(s)+R_(11) ... See the full answer