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Figure 761
(A) Perform a Dc Bias Design for the Amplifier

Question 6

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     Figure 7.6.1 (a) Perform a dc bias design for the amplifier in Fig. 7.6.1. For this purpose, assume  \beta  is very high and  V_{B E}=0.7 \mathrm{~V}  and neglect the Early effect. Design to obtain a dc base voltage of  V_{C C} / 3 , a dc emitter current of  1 \mathrm{~mA} , and a dc voltage at the collector that allows for  \pm 1-\mathrm{V}  signal swing at the collector with the minimum collector voltage no lower than  V_{B} . Use a de current in the base voltage divider of  I_{E} / 10 . What values are required for  R_{B 1}, R_{B 2}, R_{E} , and  R_{C}  ? (b) If the transistor has  \beta=100 , find the actual values obtained for  I_{E}, I_{C}, V_{B} , and  V_{C} . (c) What are the values of  g_{m}, r_{e} , and  r_{\pi}  at the dc bias point. (d) Assuming very large coupling and bypass capacitors, find the values of  R_{E 1}  and  R_{E 2}  that result in  R_{\text {in }}=10 \mathrm{k} \Omega . (e) Find the overall voltage gain  G_{v}=v_{o} / v_{\text {sig }} . (f) For  v_{o} , a sine wave with a  1-\mathrm{V}  peak amplitude, what is the peak amplitude required of the sine wave  v_{b e}  ? If this value is greater than  5 \mathrm{mV} , reduce  v_{\text {sig }}  to limit the peak amplitude of  v_{b e}  to  5 \mathrm{mV} . What is the resulting output voltage in this case?

Figure 7.6.1
(a) Perform a dc bias design for the amplifier in Fig. 7.6.1. For this purpose, assume β\beta is very high and VBE=0.7 VV_{B E}=0.7 \mathrm{~V} and neglect the Early effect. Design to obtain a dc base voltage of VCC/3V_{C C} / 3 , a dc emitter current of 1 mA1 \mathrm{~mA} , and a dc voltage at the collector that allows for ±1−V\pm 1-\mathrm{V} signal swing at the collector with the minimum collector voltage no lower than VBV_{B} . Use a de current in the base voltage divider of IE/10I_{E} / 10 . What values are required for RB1,RB2,RER_{B 1}, R_{B 2}, R_{E} , and RCR_{C} ?
(b) If the transistor has β=100\beta=100 , find the actual values obtained for IE,IC,VBI_{E}, I_{C}, V_{B} , and VCV_{C} .
(c) What are the values of gm,reg_{m}, r_{e} , and rπr_{\pi} at the dc bias point.
(d) Assuming very large coupling and bypass capacitors, find the values of RE1R_{E 1} and RE2R_{E 2} that result in Rin =10kΩR_{\text {in }}=10 \mathrm{k} \Omega .
(e) Find the overall voltage gain Gv=vo/vsig G_{v}=v_{o} / v_{\text {sig }} .
(f) For vov_{o} , a sine wave with a 1−V1-\mathrm{V} peak amplitude, what is the peak amplitude required of the sine wave vbev_{b e} ? If this value is greater than 5mV5 \mathrm{mV} , reduce vsig v_{\text {sig }} to limit the peak amplitude of vbev_{b e} to 5mV5 \mathrm{mV} . What is the resulting output voltage in this case?

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Figure 7.6.1
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Figure 7.6.2
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