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https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> oscillaotr quality factor https://designers-guide.org/forum/YaBB.pl?num=1224737462 Message started by raja.cedt on Oct 22nd, 2008, 9:51pm |
Title: oscillaotr quality factor Post by raja.cedt on Oct 22nd, 2008, 9:51pm hi , i have question regarding oscillator 1.generally Quality factor indicates slope of the phase response. ie Q=w*0.5*(dΦ/dw).can any body please explain intuitively this proportionality relation.more over i derived this relation for 2nd order.so does it applicable for other orders also,if so how to explain. Thank you |
Title: Re: oscillaotr quality factor Post by buddypoor on Oct 23rd, 2008, 12:21am 1.) The quality factor you have mentioned is defined with respect to the parasitic phase shift introducd by the amplifier - for example plus two degrees. In this case the oscillating frequency is shifted until the passive network introduces minus two degrees in order to fulfill the oscillation condition. When the phase slope is large the amplifier phase shift effect causes only a small frequency shift. This explains the proportionality between the phase slope and the definition of the so called "quality factor". 2.) However, this quality factor applies ONLY to oscillators which consist of frequency selective networks and an amplifier (two-port oscillators); thus, it applies NOT for negative resistance oscillators as well as integrator loops. 3.) Therefore, this factor has only a limited value and cannot be used to compare two-port oscillators with other types like neg. R or integrator type oscillators. |
Title: Re: oscillaotr quality factor Post by raja.cedt on Oct 23rd, 2008, 6:41am hi buddypoor, thanks for your ans.but i didn't get why Q will applicable for only two port and why not -ve resistance oscillator. I think we can treat every oscillator as -ve resistance or you can treat amp with frequency selective network EX colpits. can u tell me this one. Another question is there any chance of getting -ve Q? |
Title: Re: oscillaotr quality factor Post by buddypoor on Oct 23rd, 2008, 8:21am raja.cedt wrote on Oct 23rd, 2008, 6:41am:
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Title: Re: oscillaotr quality factor Post by raja.cedt on Oct 27th, 2008, 9:51pm hi buddypoor, Thanks for your reply.Does quality factor discussion is valid for all systems or only second order systems? Thank you. |
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