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CHAPTER 9 9.1 Since VREF= −1.25V, and vI= −1.6V, Q1is off and Q2is conducting.vC1=0 Vand vC2= −αFIEERC≅ −IEERC= −2mA()350Ω()= −0.700 V9.2 IC2IC1=exp∆VBEVT⎛ ⎝ ⎜ ⎞ ⎠ ⎟ ⇒ ∆VBE=0.025ln0.995αFIEE0.005αFIEE=0.132V(a) vI=VREF+ ∆VBE= −1.25+0.132= −1.12 VvI=VREF+ ∆VBE= −1.25−0.132= −1.38 V(b) vI=VREF+ ∆VBE= −2.00+0.132= −1.87 VvI=VREF+ ∆VBE= −2.00−0.132= −2.13 V9.3Since VREF= −2V, and vI= −1.6V, Q2is off and Q1is conducting.vC2=0 Vand vC1= −αFIEERC≅ −IEERC= −2.5mA()700Ω()= −1.75 VNote that Q1is beginning to enter the saturation region of operation, but VBC= +0.15 V is not really enough to turn on the collector-base diode. (See Problems 9.5 or 5.61.) 9.4vI=VREF+0.3V⇒Q1on; Q2off. IC1=αFIEE≅IEE=0.3mA| IC2=0vC1=0−IC1R1+RC()= −0.3mA3.33kΩ+2kΩ()= −1.60 VvC2=0−IC1R1= −0.3mA3.33kΩ()= −0.999 V9-1
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