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Unformatted text preview: Tufts University, ECE Dept.
Mar 24, 2008 EB 12: Homework # 7, Spring 2008 Due: Mar 31, 2008 1. For the series R—L—C network shown in the ﬁgure, ﬁnd the:
(a) expression for the complex impedance[Z(jw)].
(b resonant frequency where the impedance is only real. )
(c) Q of the network.
) (d draw approximate asymptotes of the magnitude and phase of the impedance versus
frequency. 2. For the Wien—Bridge oscillator shown in the ﬁgure, the ampliﬁer [Av(jw)] exhibits a
phase shift (Ada of 0.1 rad in the neighborhood of can = 1 / RC . Find the new frequency of oscillation in this case.
Hint: Find the phase sensitivity of 6(jw) in the neighborhood of we. 25w (Ito) V” R :0 3. For the Colpitt Oscillator shown in the ﬁgure:
(a) Draw the small—signal model of the oscillator. Ignore To for the BJT. (b) Find the expression for the resonant frequency. (0) Find the expression for minimum ﬂ and gm for the oscillation condition to be met. BE 12: Homework # 7 Page 2 of 2 4. The circuit shown is that of a version of Hartley Oscillator for which the small-signal
analysis has been already done in the class. (a) Choose the resonator component values for a 1—MHz oscillator.
(b) Choose the value of RE such that it is biased at IO = 1mA. (c) Use PSpice to simulate the oscillator and ﬁnd the frequency of oscillation. Brieﬂy
state the reason for any deviation of the frequency of oscillation from the calculated one. Given Values: 01 = 270pF, Cc = 0.1/iF, Vcc 2 +9V, V66 2 —9V
Note: The PSpice model for 2N2222A is provided on the web site in the homework
section. Vac ...
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This note was uploaded on 03/27/2008 for the course EE 12 taught by Professor Rout during the Spring '08 term at Tufts.
- Spring '08