For part (c) , after you calculate the new frequency of oscillation due to the spurious phase shift (as I explained in the lecture), 1. you calculate the impedance magnitude (|Z T (j ω )|) of the tuned circuit at that new frequency, and multiply it with g mQ /n to calculate the initial loop gain A e , which will be less than 3, since the |Z T (j ω )| will be less than 1 k Ω . (Or you can simply calculate how much lower the new |Z T (j ω )| is compared to the R L (1 k Ω ), and calculate the new A e by noting the A e used to be 3 when the |Z T (j ω )| used to be 1 k Ω at the old oscillation frequency). 2. From the equation for A e (= ) b ( I ) b ( I 2 b 10 ), calculate the new b, from which you now know what are new i v ) and o v ) . 3. From the new o v ) , calculate the new output power. For part (d), read the sections related to Harmonic Distortion in Oscillator_Texts.pdf. The following is a recap: As long as the total harmonic distortion is less than about 10%, the waveform distortion
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This note was uploaded on 11/22/2009 for the course EE 479 at USC.