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Unformatted text preview: nal bandwidth 20%). As a
general rule, the simple singleresonator bandpass ﬁlters only work well for fairly small fractional bandwidths
 say 10% or smaller. 53 Solution
a. The voltage gain is Av = −gm Z where Z = RC RL j ω L(j ω C )−1 . Note that the voltage gain does not
depend on any of R1 , R2 , RE , rπ , Cπ . Don’t just take my word for it  make sure that you understand this.
The voltage gain will maximize where Z  maximizes. Z is simply a parallel RLC circuit with R = RC RL =
1
833 Ω. So the voltage gain is maximum at fo = 2π√LC = 3.75 MHz.
b. Qp = 833/(2π fo L) = 1.77, so the 3 dB bandwidth is BW−3dB = fo /Qp = 3.75/1.77 = 2.12 MHz.
c. Assuming that β 1 and VBEQ = 0.7 V, then ICQ (VCC R1R1R2 − 0.7)/RE = 1.0 mA.
+ d. gn 40ICQ = 0.040 A/V. The voltage gain at resonance is −gm RC RL = −0.04(833) = 33. 3...
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This homework help was uploaded on 03/13/2014 for the course ECE 453 taught by Professor Staff during the Spring '08 term at University of Illinois, Urbana Champaign.
 Spring '08
 Staff

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